The Principle of Subsidiarity and Proportionality: Decision-Making, National Parliaments, and Judicial Review

The Principle of Subsidiarity and Proportionality: Decision-Making, National Parliaments, and Judicial Review

Introduction

The European Union is founded on a constitutional arrangement in which public authority is divided between the Union and its Member States. The Treaties confer specific competences upon the Union, but they do not establish a general power to legislate on every matter of common interest. Even where the Union possesses legal authority to act, it must exercise that authority within limits designed to preserve the autonomy of Member States, respect the diversity of national legal and political systems, and ensure that European measures do not go further than their objectives require.

Two principles are central to this arrangement: subsidiarity and proportionality. Both are set out in Article 5 of the Treaty on European Union (TEU), alongside the principle of conferral. They regulate not simply whether the Union has a competence, but how that competence may legitimately be exercised.

Subsidiarity addresses the question of which level of government should act. It requires the Union, in areas where it does not possess exclusive competence, to demonstrate that the objectives of a proposed measure cannot be sufficiently achieved by the Member States acting at national, regional, or local level, and that those objectives can be better achieved at Union level because of the scale or effects of the proposed action.

Proportionality addresses a different question: how far should public intervention go? It requires the content and form of Union action not to exceed what is necessary to achieve the objectives established by the Treaties. A measure may pursue a legitimate European objective and still be disproportionate if it imposes unnecessary restrictions, excessive burdens, or obligations that are not adequately connected to the result sought.

These principles are therefore not technical formalities. They are constitutional safeguards governing the exercise of public power in a multilevel legal order. They influence the preparation of legislation by the European Commission, the scrutiny exercised by national parliaments, the deliberations of the European Parliament and the Council, and the judicial review conducted by the Court of Justice of the European Union.

The Treaty of Lisbon strengthened their practical significance by introducing more structured procedures for national parliamentary scrutiny. Protocol No 2 on the Application of the Principles of Subsidiarity and Proportionality establishes requirements for legislative proposals, provides national parliaments with a formal opportunity to issue reasoned opinions, and creates procedures commonly known as the yellow-card and orange-card mechanisms.

Nevertheless, the operation of these principles raises difficult questions. How should the Union establish that national action is insufficient? What evidence is required to demonstrate European added value? How much discretion should the political institutions enjoy when assessing complex economic, environmental, or social problems? When does a regulatory measure become excessive? And to what extent can the Court of Justice intervene in policy choices made by the Union legislature?

Understanding subsidiarity and proportionality requires examining them both as legal standards and as instruments of institutional decision-making. Together, they express an important constitutional proposition: the existence of a European competence does not mean that every possible exercise of that competence is justified.

1. The Constitutional Foundations of Subsidiarity and Proportionality

The legal foundations of both principles are found in Article 5 TEU. The structure of that provision is important because it establishes a sequence of constitutional questions rather than treating the principles as interchangeable limitations.

Article 5(1) states that the limits of Union competences are governed by conferral, while the exercise of those competences is governed by subsidiarity and proportionality. Article 5(2) defines conferral: the Union may act only within the competences attributed to it by the Treaties, and competences not conferred remain with the Member States.

Article 5(3) then establishes subsidiarity. In areas outside the Union’s exclusive competence, the Union may act only where two conditions are satisfied:

• The objectives of the proposed action cannot be sufficiently achieved by the Member States, whether acting at central, regional, or local level.
• Those objectives can, because of the scale or effects of the proposed action, be better achieved at Union level.

Article 5(4) establishes proportionality: the content and form of Union action must not exceed what is necessary to achieve the objectives of the Treaties.

The distinction between these provisions is fundamental. Conferral asks whether the Union possesses the relevant competence at all. Subsidiarity asks whether exercising a non-exclusive competence at Union level is justified. Proportionality asks whether the particular measure, once the Union has decided to act, is appropriately limited.

A proposal may therefore encounter three different legal difficulties. It may lack a valid Treaty legal basis; it may concern a matter in which Union action is not justified because Member States can sufficiently achieve the objective; or it may pursue a legitimate objective through measures that go further than necessary. Each problem concerns a different stage of constitutional assessment.

The principles apply to all Union institutions. Protocol No 2 expressly requires each institution to ensure their constant observance. They are therefore relevant not only when the Commission drafts a proposal, but also when the European Parliament and Council amend, negotiate, and adopt legislation, and when institutions exercise powers under the Treaties.

The principles must also be understood in the context of Article 10(3) TEU, which provides that decisions are to be taken as openly and as closely as possible to citizens. Subsidiarity gives legal expression to this idea of proximity, although proximity is not an absolute rule requiring every decision to be made at the lowest possible administrative level. The Treaty instead requires a reasoned assessment of whether the relevant objective can be achieved sufficiently at that level and whether Union action would achieve it more effectively.

The primary legal texts are available in the consolidated Treaty on European Union, Article 5 and Protocol No 2. EUR-Lex+1

2. The Principle of Subsidiarity: Choosing the Appropriate Level of Action

2.1 Meaning and constitutional purpose

Subsidiarity is concerned with the allocation of decision-making between different levels of government. Its central proposition is that public decisions should ordinarily be taken by the level of authority capable of addressing the relevant problem effectively, while Union intervention is justified where the objectives cannot be sufficiently achieved by Member States acting independently and can be better achieved collectively.

The principle has both a restrictive and an enabling dimension.

Its restrictive dimension protects the Member States against unnecessary intervention by the Union. The existence of a shared competence does not automatically justify European legislation. The Union must explain why national, regional, or local action would be insufficient in the circumstances.

Its enabling dimension recognises that some problems cannot be effectively addressed through isolated national measures. Economic activity, environmental systems, digital networks, cross-border crime, transport infrastructure, and public health risks may extend beyond national borders. Where the scale or effects of a problem make coordinated European action more effective, subsidiarity can support intervention at Union level.

The principle is therefore not simply an instrument for decentralisation. Nor does it establish a presumption that national action is always preferable. It is a test of the appropriate level of action in light of the objective and the practical characteristics of the problem.

2.2 The scope of subsidiarity

Subsidiarity applies in areas where the Union does not have exclusive competence. It is particularly significant in fields of shared competence under Article 4 TFEU, including the internal market, social policy within the limits defined by the Treaties, economic, social and territorial cohesion, agriculture and fisheries, the environment, consumer protection, transport, energy, and the area of freedom, security and justice.

In areas of exclusive Union competence, the Union does not have to establish that Member States would be unable to achieve the relevant objective independently. The Treaties have already allocated the competence to the Union. The exercise of that competence remains subject to proportionality and other applicable legal constraints.

This distinction is important because subsidiarity does not determine the existence or extent of a competence. It governs the exercise of non-exclusive competences. A measure cannot be justified merely by invoking subsidiarity if the Union lacks a valid legal basis in the Treaties.

The principle also does not apply in precisely the same way to supporting, coordinating, or supplementary competences under Article 6 TFEU. In those fields, the Treaties define the Union’s role differently and generally prevent harmonisation of national laws where the Treaties so provide. The precise legal basis and the nature of the Union’s power must therefore be identified before applying the subsidiarity analysis.

2.3 The two substantive requirements

Article 5(3) TEU contains two connected requirements.

The first is the insufficiency of Member State action. The proposed objective must not be capable of being sufficiently achieved by Member States acting at national, regional, or local level. This assessment must consider the actual problem, not merely the political preference for common European rules.

The second is comparative effectiveness at Union level. Even if national action is insufficient, it must also be established that the objective can be better achieved at Union level because of the scale or effects of the proposed action.

These requirements are related but distinct. A problem may be difficult for individual Member States to solve, yet a particular European measure may not provide an effective solution. Conversely, the existence of cross-border effects may make European coordination useful, but it does not automatically establish that every element of a proposed legislative scheme should be regulated centrally.

A sound subsidiarity assessment should therefore identify the problem, explain the limitations of national action, and demonstrate the added value expected from Union intervention.

2.4 Scale, effects, and European added value

The references to the scale and effects of the proposed action require a practical assessment. Relevant considerations may include:

• whether the problem crosses national borders;
• whether different national rules create obstacles to the internal market;
• whether unilateral national measures produce inconsistent or conflicting outcomes;
• whether the activity concerned depends on networks or systems operating across the Union;
• whether coordinated action would reduce regulatory fragmentation;
• whether the consequences of national inaction would affect other Member States;
• whether common standards would produce benefits that isolated national measures could not reasonably deliver.

Environmental protection provides a clear illustration. Pollution may originate in one state and affect the territory or population of another. A purely national approach may be insufficient where the source, movement, and consequences of the pollution are transboundary. Union action may provide common standards, coordinated monitoring, and shared obligations.

The internal market offers another example. If incompatible national technical requirements prevent goods or services from circulating freely, separate national solutions may preserve the very barriers that the Treaties seek to remove. Common rules may be more effective because the objective concerns the operation of the market as a whole.

However, the existence of a cross-border dimension is not conclusive. The Union must still explain why the particular proposed measure is better suited to achieving the objective. European added value cannot be established simply by asserting that a matter is important to the Union.

The European Parliament’s explanation of subsidiarity identifies the three central considerations as non-exclusive competence, the insufficiency of Member State action, and the comparative advantages of Union action. European Parliament+1

3. The Principle of Proportionality: Limiting the Intensity of Union Action

3.1 Meaning and legal function

Where subsidiarity determines whether action should be taken at Union level, proportionality determines the permissible intensity and design of that action.

Article 5(4) TEU requires that the content and form of Union action do not exceed what is necessary to achieve the objectives of the Treaties. The principle applies to legislative measures, administrative decisions, regulatory requirements, and other exercises of Union authority.

Proportionality is a general principle of EU law and operates beyond the specific context of the relationship between Union and Member State competences. It can be relevant where a Union institution imposes obligations on individuals or businesses, restricts economic activity, adopts sanctions, or exercises discretionary powers.

Its constitutional purpose is to prevent public authority from using measures that are excessive in relation to the legitimate objective pursued. The Union may pursue ambitious objectives, but the means selected must remain legally connected to those objectives and must not impose unnecessary restrictions.

Proportionality is not a requirement that Union action be minimal in every case. A measure may impose substantial obligations where those obligations are justified by the importance of the objective and the absence of an equally effective, less restrictive alternative. The principle instead requires a reasoned relationship between the objective, the means, and the burdens imposed.

3.2 The three-stage test

The Court of Justice commonly analyses proportionality through three connected questions: suitability, necessity, and proportionality in the strict sense. The precise formulation may vary according to the legal context, but the structure provides a useful framework.

Suitability

A measure must be appropriate for achieving the legitimate objective pursued. It must be capable of contributing to that objective in a coherent and rational manner.

For example, if the Union adopts common technical standards to remove barriers to trade, the standards should genuinely contribute to reducing incompatible national requirements. A measure unrelated to the identified problem, or incapable of producing the intended effect, may fail the suitability requirement.

Suitability does not necessarily require a measure to achieve its objective immediately or completely. Legislative measures often operate in complex social and economic environments, and their effects may depend on implementation, compliance, and changing circumstances. The question is whether the measure is reasonably capable of advancing the stated objective.

Necessity

A measure must not go beyond what is necessary to achieve its objective. Where several measures are capable of achieving the same legitimate objective, the institutions should consider whether a less restrictive alternative would be equally effective.

For example, a Union regulation might impose a uniform technical requirement on all businesses operating in a particular sector. If the same objective could be achieved through a less burdensome system of mutual recognition, targeted obligations, or minimum standards, the more restrictive approach may require additional justification.

The availability of an alternative is not sufficient by itself to establish a violation. The alternative must be realistically capable of achieving the objective with comparable effectiveness. A less restrictive measure that would materially weaken the protection sought may not be a legally equivalent alternative.

Proportionality in the strict sense

The final stage concerns the relationship between the benefits of the measure and the disadvantages or burdens it creates. Even a measure that is suitable and necessary may impose consequences that are excessive when assessed against the objective pursued.

This stage is particularly important where legislation affects fundamental rights, imposes substantial financial obligations, restricts professional or commercial activity, or creates significant administrative burdens.

The assessment may require consideration of the seriousness of the objective, the expected benefits, the extent of the interference, the persons affected, and the availability of safeguards or exceptions.

The three stages should not be treated as a mechanical formula. The Court’s approach depends on the legal basis, the nature of the measure, the rights affected, and the degree of discretion enjoyed by the institution concerned.

3.3 The form of Union action

Proportionality also concerns the form of the measure. Article 296 TFEU and Article 5 of Protocol No 2 must be read in conjunction with Article 5(4) TEU.

The Union may choose among different legal instruments, including regulations, directives, and decisions under Article 288 TFEU. A regulation is binding in its entirety and directly applicable in all Member States. A directive binds each Member State as to the result to be achieved but leaves national authorities the choice of form and methods. A decision is binding in its entirety and, where it specifies addressees, is binding only upon them.

The choice between these instruments may affect the degree of national discretion and the intensity of European intervention. A regulation may be appropriate where uniform rules are essential. A directive may be more suitable where a common result is required but national legal systems should retain flexibility in implementation.

The choice of instrument is not determined by proportionality alone. It must also comply with the relevant Treaty legal basis and the institutional procedures attached to it. Nevertheless, proportionality requires the institutions to consider whether the chosen form is appropriate to the objective and whether it imposes unnecessary constraints.

3.4 Administrative and financial burdens

Protocol No 2 expressly requires attention to the financial and administrative consequences of draft legislative acts. Article 5 provides that proposals should contain an assessment of their financial impact and, in the case of directives, their implications for national and, where necessary, regional legislation.

The Protocol also requires the institutions to consider burdens falling upon the Union, national governments, regional and local authorities, economic operators, and citizens. Such burdens should be minimised and commensurate with the objective pursued.

This requirement makes proportionality relevant to the practical architecture of legislation. A measure may pursue a legitimate policy objective but still create unnecessary reporting obligations, excessive compliance costs, duplicated procedures, or disproportionate demands upon smaller authorities and businesses.

For this reason, proportionality is connected with impact assessment, consultation, regulatory simplification, and the evaluation of existing legislation. It requires institutions to consider not only what a measure is intended to achieve, but also the costs and constraints through which it operates. EUR-Lex+1

4. Subsidiarity and Proportionality Compared

Although the principles are closely connected, they perform different legal functions. Confusing them can lead to an incorrect analysis of the validity of Union legislation.

Principle	Main question	Central legal concern
Conferral	Does the Union possess the competence?	Treaty limits on Union authority
Subsidiarity	Should the Union exercise a non-exclusive competence in this matter?	Appropriate level of decision-making
Proportionality	Does the measure go further than necessary?	Appropriate intensity and form of intervention

Consider a hypothetical proposal to regulate the safety of cross-border digital services.

The first question is whether the Treaties confer a legal basis enabling the Union to regulate the matter. This is an issue of conferral.

If a valid shared competence exists, the next question is whether Member States could sufficiently achieve the objectives independently, or whether the cross-border nature of the services makes common European action more effective. This is the subsidiarity assessment.

If Union action is justified, the institutions must then decide what obligations are required. Should the measure impose uniform rules on every service provider? Should it apply only to services presenting specified risks? Could reporting obligations be simplified? Could smaller providers be subject to proportionate requirements? These questions concern proportionality.

A measure might therefore satisfy conferral but fail subsidiarity. It might satisfy both conferral and subsidiarity but fail proportionality. Equally, it may satisfy all three principles while remaining subject to other Treaty requirements, fundamental rights, procedural rules, and judicial review.

The principles are cumulative safeguards. None can replace another.

5. Protocol No 2: The Procedural Framework

The Treaty provisions establish the constitutional principles, while Protocol No 2 sets out procedures intended to ensure that those principles influence the legislative process from its earliest stages.

The Protocol is legally binding and applies to the Union institutions. It does not merely recommend that institutions consider subsidiarity and proportionality; it creates specific procedural obligations concerning consultation, justification, parliamentary scrutiny, and review.

5.1 Consultation before legislative proposals

Article 2 of Protocol No 2 requires the Commission to consult widely before proposing legislative acts. Where appropriate, consultations must take account of the regional and local dimension of the action envisaged.

This requirement is significant because subsidiarity cannot be properly assessed solely from the perspective of central national governments or Union institutions. The capacity of regional and local authorities may be relevant to whether a problem can be sufficiently addressed without Union intervention.

The Protocol recognises an exception for exceptional urgency. In such circumstances, the Commission may omit consultation, but it must explain the reasons for doing so in its proposal.

Consultation does not transfer legislative authority to stakeholders or regional institutions. It provides information that can help the Commission assess the nature of the problem, the available regulatory alternatives, and the likely effects of intervention at different levels.

5.2 The obligation to provide a detailed statement

Article 5 of Protocol No 2 requires draft legislative acts to be justified with regard to subsidiarity and proportionality. Each draft should contain a detailed statement that makes it possible to assess compliance with both principles.

The statement should address:

1. The financial impact of the proposal.
2. The implications for national legislation and, where necessary, regional legislation, particularly where a directive is proposed.
3. The reasons why the objectives can be better achieved at Union level.
4. Qualitative and, wherever possible, quantitative indicators supporting that conclusion.
5. The need to minimise financial and administrative burdens and ensure that they remain commensurate with the objective.

These requirements are intended to make the reasoning behind Union intervention visible and open to scrutiny.

A statement that merely repeats the language of Article 5 TEU is unlikely to provide a meaningful explanation. The institutions should identify the problem, explain the limits of national action, and provide a reasoned account of the advantages expected from Union-level intervention.

The statement also serves an institutional purpose. It gives national parliaments a basis for evaluating a proposal within the eight-week period, enables the Union legislature to assess the justification for action, and may later assist the Court of Justice when reviewing the legality of the adopted measure.

5.3 The role of impact assessments

Impact assessments are an important practical instrument for applying the principles, although they are not a substitute for the legal test.

An impact assessment may examine the problem that the proposed legislation seeks to address, the consequences of taking no action, the available policy options, the likely economic and social effects, environmental implications, administrative costs, and the distribution of burdens among affected groups.

In subsidiarity terms, it can help establish why national measures are insufficient and what additional benefits European action may produce. In proportionality terms, it can help compare alternative measures and identify whether a less burdensome option could achieve the same objective.

The quality of the analysis matters. Quantitative indicators can be useful, but not every legal or policy objective can be reduced to numerical measurement. Qualitative evidence, institutional experience, cross-border assessments, and reasoned predictions may also be relevant.

An impact assessment should therefore be understood as an evidential and analytical instrument. It supports the institutions’ reasoning but does not automatically establish that the final measure complies with the Treaties.

The relevant procedural requirements are set out in Protocol No 2, Articles 1–5. EUR-Lex+1

6. National Parliaments and the Early Warning Mechanism

6.1 The constitutional role of national parliaments

The Treaty of Lisbon strengthened the position of national parliaments in EU decision-making. Article 12 TEU recognises their contribution to the proper functioning of the Union, including through their participation in the procedures established by the Treaties.

Their role is particularly important in relation to subsidiarity. National parliaments are constitutionally connected to the democratic systems of the Member States and can scrutinise whether a proposed measure should be adopted at Union level rather than addressed through national legislation or other domestic action.

This role does not give national parliaments a general veto over European legislation. They cannot reject a proposal merely because they disagree with its political objectives or regulatory approach. Their specific power under Protocol No 2 concerns compliance with subsidiarity.

They may, however, express broader political concerns through other forms of parliamentary dialogue with the Union institutions. The distinction between a formal reasoned opinion under Protocol No 2 and an ordinary political opinion is important because only the former counts towards the thresholds of the early warning mechanism.

6.2 The eight-week period

Article 6 of Protocol No 2 gives each national parliament, or each chamber in a bicameral system, eight weeks from the date of transmission of a draft legislative act to send a reasoned opinion.

The opinion must explain why the parliament considers that the draft does not comply with subsidiarity. It is sent to the Presidents of the European Parliament, the Council, and the Commission.

Where appropriate, national parliaments may consult regional parliaments with legislative powers. This is significant in Member States where constitutional arrangements allocate legislative responsibilities to subnational institutions. The subsidiarity assessment may require attention to the actual distribution of domestic powers rather than treating the Member State as a single, centralised decision-making authority.

The eight-week period is intended to provide a meaningful opportunity for parliamentary scrutiny while allowing the Union legislative process to continue. It also creates practical challenges: national parliaments must examine complex proposals, obtain expert advice, coordinate internally, and formulate legally reasoned opinions within a relatively short period.

6.3 Allocation of votes

Each national parliament is allocated two votes. In a bicameral parliamentary system, each chamber receives one vote.

With 27 Member States, the total number of votes is 54. The distribution is designed to ensure that parliamentary scrutiny reflects the constitutional structure of the Member States, rather than simply counting national governments.

The vote allocation is important because the yellow-card and orange-card mechanisms are triggered by the number of votes represented by reasoned opinions, not merely by the number of parliaments that express concern.

6.4 The yellow-card procedure

Under Article 7(2) of Protocol No 2, where reasoned opinions represent at least one third of the votes allocated to national parliaments, the draft legislative act must be reviewed.

For proposals relating to the area of freedom, security and justice submitted under Article 76 TFEU, the threshold is reduced to one quarter.

This procedure is commonly known as the yellow card.

Following review, the institution responsible for the proposal may decide to maintain it, amend it, or withdraw it. If it maintains the proposal, it must explain its reasons.

The yellow card does not automatically terminate the legislative process. It requires reconsideration and a reasoned response. Its constitutional importance lies in compelling the proposing institution to address substantial parliamentary objections rather than treating them as irrelevant political commentary.

6.5 The orange-card procedure

Article 7(3) establishes a stronger mechanism for proposals subject to the ordinary legislative procedure.

Where reasoned opinions represent a simple majority of the votes allocated to national parliaments, the Commission must review the proposal. If it decides to maintain it, it must explain why it considers the proposal consistent with subsidiarity.

The proposal and the Commission’s justification are then submitted to the Union legislature. Before concluding the first reading, the European Parliament and the Council consider whether the proposal is compatible with subsidiarity.

If 55% of the members of the Council or a majority of the votes cast in the European Parliament consider that the proposal breaches subsidiarity, it is not to be given further consideration.

This is known as the orange card.

The orange card is therefore more consequential than the yellow card, but it remains part of the legislative process rather than a general power of national parliamentary veto. Its operation depends on the proposal being subject to the ordinary legislative procedure and on the relevant institutional majorities being reached.

6.6 Political dialogue beyond the formal mechanism

National parliaments may communicate with the Commission on EU policy and legislative proposals even where the thresholds for a yellow or orange card are not reached.

This broader political dialogue allows national parliaments to express concerns, request explanations, and contribute to discussions about the design of European legislation.

It is important to distinguish this dialogue from the formal early warning system. A parliament may raise substantive concerns about a proposal without issuing a reasoned opinion that counts towards the Protocol’s thresholds. Equally, a reasoned opinion may contribute to the political debate even where it does not trigger a formal review.

The Commission’s account of the mechanism explains the allocation of votes, the eight-week period, and the consequences of the yellow and orange cards. European Commission+2

7. Judicial Review of Subsidiarity and Proportionality

7.1 The Court of Justice as constitutional guardian

Political scrutiny does not replace judicial review. The Court of Justice of the European Union has jurisdiction to examine whether Union acts comply with the Treaties, including the principles of subsidiarity and proportionality.

The legal framework for review is found principally in Article 263 TFEU, which provides for actions seeking the annulment of Union acts intended to produce legal effects, and Article 267 TFEU, which allows national courts to refer questions concerning the validity and interpretation of EU law to the Court of Justice.

The Court may therefore assess subsidiarity and proportionality through direct actions brought by privileged or eligible applicants, or through preliminary references from national courts.

Article 8 of Protocol No 2 specifically confirms the Court’s jurisdiction over actions based on infringement of subsidiarity by a legislative act. Such actions may be brought under Article 263 TFEU by a Member State, or notified by it in accordance with its legal order on behalf of its national parliament or a chamber of that parliament.

The Protocol also recognises the role of the European Committee of the Regions in challenging legislative acts where the Treaties require its consultation.

7.2 Review of the duty to state reasons

The obligation to justify a measure is a central part of judicial scrutiny.

Article 296 TFEU requires Union legal acts to state the reasons on which they are based. The statement of reasons must disclose the essential reasoning of the institution, allowing affected persons and the courts to understand the measure and assess its legality.

In subsidiarity cases, the Court examines whether the reasons provided make it possible to understand why the Union considered action at European level justified.

The Court does not necessarily require a separate, exhaustive essay on subsidiarity in every legislative act. The reasoning may be assessed by reference to the recitals, the context of the measure, and the circumstances surrounding its adoption. However, the essential justification must be sufficiently clear to permit meaningful review.

This is not merely a question of drafting style. An inadequate explanation may prevent national parliaments, legislators, affected persons, and courts from evaluating whether the Treaty requirements have been respected.

7.3 The limits of judicial intervention

The Court recognises that legislative institutions often make complex political, economic, and social assessments. In such circumstances, they may enjoy a broad margin of discretion.

This is particularly relevant where legislation concerns technical regulation, economic policy, public health, environmental protection, or the operation of the internal market. The Court does not generally replace the legislature’s assessment with its own preferred policy solution.

That does not mean that the institutions enjoy unlimited discretion. The Court may examine whether the relevant evidence and reasoning support the conclusion that Union action was justified, whether the measure is manifestly inappropriate, and whether the institutions have complied with the procedural and substantive requirements imposed by the Treaties.

The intensity of review depends on the nature of the decision and the legal interests affected. Where fundamental rights are seriously restricted, the proportionality assessment may require particularly careful examination of the justification and safeguards.

Judicial restraint and effective review are therefore not opposites. The Court can respect the political discretion of the legislature while ensuring that its decisions remain within the legal boundaries established by the Treaties.

8. Important Case Law

The Court’s judgments provide practical illustrations of how subsidiarity and proportionality operate in the EU legal order.

8.1 United Kingdom v Council (Working Time Directive), Case C-84/94

In United Kingdom v Council, the United Kingdom challenged the validity of the Working Time Directive, including its legal basis and compatibility with subsidiarity.

The Court rejected the challenge. The judgment is important because it addressed subsidiarity in the context of EU social policy and recognised that the principle was relevant to the exercise of Community powers.

The Court’s reasoning also illustrates the connection between subsidiarity and the duty to state reasons. The justification for Union action may be assessed through the reasoning expressed in the measure itself and its legislative context.

The case is useful for understanding that subsidiarity is not a general political objection to harmonisation. It requires an examination of whether the Treaty conditions for Union action are satisfied.

Official judgment: Case C-84/94, United Kingdom v Council.

8.2 Germany v European Parliament and Council, Case C-233/94

In Germany v European Parliament and Council, Germany challenged the directive establishing deposit-guarantee schemes for credit institutions.

The Court considered the legal basis and the justification for European action. The case contributed to the development of judicial reasoning on subsidiarity and the requirement that legislative measures explain why action at Union level is appropriate.

Together, United Kingdom v Council and Germany v Parliament and Council are important early authorities demonstrating that subsidiarity is judicially reviewable and connected with the obligation to state reasons.

Official judgment: Case C-233/94, Germany v Parliament and Council.

8.3 Vodafone and Others, Case C-58/08

The judgment in Vodafone and Others concerned the EU regulation of roaming charges on public mobile telephone networks.

Mobile telecommunications operated across national borders, and the pricing of wholesale and retail roaming services created a problem that could not be effectively addressed through isolated national measures. The Court examined the regulation’s legal basis and the objections based on subsidiarity and proportionality.

It accepted that the Union legislature could conclude that a common approach was necessary because of the interdependence between wholesale and retail roaming charges. A purely national approach would not have achieved the same result in a market operating across the Union.

The Court also reaffirmed that, where the legislature makes complex economic and political choices, it enjoys broad discretion. A measure will not generally be invalid merely because another regulatory approach might have been preferable. In the relevant context, the question included whether the measure was manifestly inappropriate in relation to its objective.

The judgment is particularly instructive because it demonstrates how the two principles can operate together. Subsidiarity supported intervention at Union level, while proportionality governed the extent and design of the regulation.

Official judgment: Case C-58/08, Vodafone and Others. EUR-Lex+1

8.4 Philip Morris Brands and Others, Case C-547/14

In Philip Morris Brands and Others, the Court considered the validity of the Tobacco Products Directive, including objections concerning subsidiarity and proportionality.

The legislation sought to approximate national rules governing the manufacture, presentation, and sale of tobacco products. The Court examined whether the Union legislature was entitled to conclude that the objectives could be better achieved at Union level.

The judgment is significant for its treatment of the detailed statement required by Protocol No 2. The Court explained that compliance with the duty to give reasons must be assessed not only by looking at the wording of the contested measure but also by considering its context and the circumstances of the case.

The Court’s approach reflects the practical difficulty of evaluating subsidiarity in a complex regulatory environment. The legislature must provide a reasoned basis for its conclusion, but judicial review takes account of the legislative context and the discretion available to the institutions.

Official judgment: Case C-547/14, Philip Morris Brands and Others. European Parliament

8.5 Jippes and Others, Case C-189/01

The case of Jippes and Others concerned measures adopted in response to the outbreak of foot-and-mouth disease and included an examination of proportionality.

The Court reiterated that, in areas involving complex assessments and policy choices, the Union legislature and institutions may enjoy broad discretion. Judicial review does not ordinarily require the Court to determine whether the measure was the only possible or the best conceivable solution.

However, the exercise of discretion remains subject to legal limits. The measure must not be manifestly inappropriate in relation to the objective pursued, and the institutions must act within the requirements of proportionality.

The case illustrates why the standard of judicial review may differ according to the technical and policy complexity of the subject matter.

Official judgment: Case C-189/01, Jippes and Others.

9. The Relationship Between Political Accountability and Judicial Review

Subsidiarity and proportionality operate through two complementary forms of control.

The first is political and institutional. The Commission must justify its proposals, national parliaments may issue reasoned opinions, and the European Parliament and Council must consider the legal and policy arguments presented during the legislative process.

The second is judicial. The Court of Justice may determine whether an adopted measure complies with the Treaties and whether the institutions have remained within the limits of their legal powers.

These forms of control serve different purposes.

Political scrutiny allows disagreement to be expressed before legislation is adopted. It can encourage the Commission to reconsider a proposal, provide further evidence, narrow its scope, or withdraw it. It is preventive and deliberative.

Judicial review examines the legality of an act after it has been adopted, or its validity when challenged through the procedures available under EU law. It is concerned with legal compliance rather than political preference.

Neither mechanism is a complete substitute for the other. A proposal may survive the early warning mechanism because the required parliamentary threshold is not reached, yet still be challenged before the Court. Conversely, a large number of reasoned opinions may lead to political reconsideration without necessarily establishing that the proposal would be unlawful.

The system is designed to ensure that the principles are considered throughout the legislative process, rather than only after a dispute reaches a court.

10. Practical Examples of the Two Principles

The principles become easier to understand when applied to different categories of regulation.

10.1 Environmental protection

Suppose a proposed measure seeks to reduce pollution affecting several Member States.

Subsidiarity requires an assessment of whether national measures can sufficiently achieve the objective. If pollution crosses borders, national action may be unable to prevent environmental harm originating elsewhere. Common standards and coordinated monitoring may provide clear advantages at Union level.

Proportionality then requires examination of the regulatory design. The Union may need common emissions limits, monitoring obligations, or enforcement standards. However, it should consider whether all proposed requirements are necessary, whether differentiated implementation arrangements are justified, and whether the financial and administrative burdens are commensurate with the environmental objective.

10.2 Consumer protection in the internal market

Imagine that different national consumer-protection rules create uncertainty for businesses and consumers engaged in cross-border transactions.

Subsidiarity may support Union action where regulatory fragmentation prevents consistent protection or obstructs the functioning of the internal market.

Proportionality would require consideration of the appropriate degree of harmonisation. Full uniformity may be justified where divergent rules create serious barriers, but minimum harmonisation or targeted common standards may be more appropriate in other circumstances.

10.3 Public health emergencies

A health emergency may have consequences extending beyond the territory of one Member State. Cross-border transmission, movement of people, supply chains, and the availability of medical resources may make coordination necessary.

Subsidiarity would examine whether national responses alone can sufficiently achieve the relevant objective and whether Union coordination provides additional effectiveness.

Proportionality would then examine the nature and duration of the measures, the rights affected, the restrictions imposed, and whether less restrictive alternatives could achieve comparable protection.

The existence of an emergency does not remove the obligation to comply with the Treaties. Urgency may affect the factual assessment and the procedures available, but it does not create an unlimited Union competence.

10.4 Digital regulation

Digital services often operate across borders, while national rules may differ considerably. A common European framework may reduce fragmentation and provide consistent standards.

Subsidiarity asks whether national approaches can sufficiently address the problem and whether a common framework offers demonstrable advantages.

Proportionality asks whether the regulatory obligations are appropriately tailored. Reporting requirements, compliance systems, technical standards, and enforcement mechanisms should be designed with attention to the objective, the risks addressed, and the burdens imposed.

These examples demonstrate that subsidiarity and proportionality are not abstract constitutional slogans. They require institutions to connect legal authority with evidence, regulatory design, and the real consequences of public intervention.

11. Challenges and Limitations in the Application of the Principles

Despite their constitutional importance, subsidiarity and proportionality are not always straightforward to apply. Their effectiveness depends partly on the quality of institutional reasoning and partly on the willingness of political and judicial institutions to examine that reasoning critically.

11.1 The difficulty of measuring European added value

Subsidiarity requires a comparison between national and European action. In practice, however, it may be difficult to determine whether an objective can be sufficiently achieved by Member States acting independently.

Some problems have clearly identifiable cross-border consequences. Others involve a combination of domestic and European dimensions. For example, consumer protection may concern transactions within a single Member State while also affecting businesses and consumers operating across the internal market.

The assessment of European added value may involve predictions about future economic behaviour, administrative efficiency, technological development, and regulatory effects. Such predictions cannot always be established with mathematical certainty.

This creates a risk that subsidiarity assessments become formulaic. Institutions may invoke the general desirability of common European rules without sufficiently explaining why national action would be inadequate. The detailed statement required by Protocol No 2 is intended to reduce this risk, but the quality of the reasoning remains essential.

11.2 The margin of discretion enjoyed by the legislature

The Court’s recognition of broad legislative discretion in complex policy areas creates another difficulty. The institutions may rely on economic, scientific, or social assessments that involve uncertainty and competing objectives.

Judicial review must respect the institutional role of the legislature, but excessive deference could weaken the practical protection offered by proportionality and subsidiarity.

The legal challenge is to distinguish legitimate legislative discretion from an exercise of authority that lacks sufficient justification or exceeds the limits established by the Treaties.

11.3 National parliamentary scrutiny and institutional capacity

The early warning mechanism gives national parliaments a formal role, but the practical effectiveness of that role depends on their resources and internal procedures.

The eight-week period may be demanding when a proposal is technically complex, politically sensitive, or accompanied by extensive supporting documentation. Parliamentary committees must have sufficient expertise and time to examine the proposal and coordinate with other institutions where necessary.

There is also a difference between the constitutional power to issue a reasoned opinion and the political ability to coordinate objections across several Member States. The yellow-card threshold requires a substantial level of collective parliamentary engagement.

11.4 Subsidiarity is not a general political veto

A further limitation concerns the nature of the principle itself. Subsidiarity is a legal standard, not a general instrument for rejecting policies that a national parliament or government dislikes.

A proposal may be politically controversial while remaining consistent with subsidiarity. Conversely, a policy that enjoys broad political support may still be unlawful if the conditions for Union intervention are not satisfied.

The legal assessment must therefore remain focused on competence, the insufficiency of national action, European added value, and the evidence supporting the proposed measure.

12. A Practical Method for Assessing an EU Legislative Proposal

For legal analysis, academic research, or parliamentary scrutiny, the following sequence provides a useful method for examining whether a proposed Union measure complies with the principles.

First: Identify the legal basis.

Determine the Treaty provision relied upon and establish whether it confers the relevant competence upon the Union. A measure cannot be justified through subsidiarity or proportionality if the Union lacks the necessary competence.

Second: Determine the category of competence.

Establish whether the matter falls within exclusive, shared, or supporting, coordinating, and supplementary competence. This determines whether subsidiarity applies and what limits govern the Union’s action.

Third: Identify the objective and the problem.

The institutions should explain what problem the proposal seeks to address and how the proposed measure contributes to the objectives established by the Treaties.

Fourth: Apply the subsidiarity test.

Ask whether Member States can sufficiently achieve the objective at national, regional, or local level. If not, identify why action at Union level would be more effective because of the scale or effects of the proposed measure.

Fifth: Examine the supporting evidence.

Consider whether the impact assessment, consultation results, economic data, scientific material, and explanatory statement support the conclusion that Union intervention is justified.

Sixth: Apply the proportionality test.

Assess whether the proposed measure is suitable, necessary, and appropriately balanced in relation to its objective. Consider whether a less restrictive alternative could achieve the same result with comparable effectiveness.

Seventh: Examine the form of the measure.

Consider whether the choice of regulation, directive, or decision is appropriate and whether national authorities retain an appropriate degree of discretion.

Eighth: Examine the procedural safeguards.

Check whether the requirements of Protocol No 2 have been observed, including consultation, the detailed statement, and transmission of the proposal to national parliaments.

Ninth: Consider parliamentary and judicial scrutiny.

Determine whether national parliaments have issued reasoned opinions and whether any formal review mechanism has been triggered. If the measure has been adopted, consider whether it may be challenged under Article 263 or its validity raised through Article 267 TFEU.

This method separates the constitutional questions that are frequently confused in discussions of EU legislative power. It also makes clear that the validity of a measure depends not merely on its policy objective, but on the legal authority, reasoning, evidence, and regulatory design supporting it.

13. Key Takeaways

1. Subsidiarity and proportionality are constitutional principles governing the exercise of EU competences under Article 5 TEU.
2. They operate alongside the principle of conferral, which determines the limits of Union authority.
3. Conferral asks whether the Union possesses the competence to act.
4. Subsidiarity determines whether action at Union level is justified in areas outside exclusive Union competence.
5. Proportionality determines whether the content and form of Union action exceed what is necessary.
6. Subsidiarity applies particularly to shared competences, where both the Union and Member States possess legislative authority within the limits established by the Treaties.
7. The Union must demonstrate that Member States cannot sufficiently achieve the proposed objective and that Union action can achieve it better because of the scale or effects of the proposed measure.
8. Subsidiarity does not establish an automatic preference for national action. It requires an assessment of the most appropriate level of intervention.
9. Proportionality is commonly examined through suitability, necessity, and proportionality in the strict sense.
10. The choice between regulations, directives, and decisions may be relevant to proportionality.
11. Protocol No 2 requires the institutions to justify draft legislative acts with regard to subsidiarity and proportionality.
12. The Commission must consult widely before proposing legislative acts, taking regional and local considerations into account where appropriate.
13. Legislative proposals should include a detailed statement addressing their financial impact, regulatory consequences, and European added value.
14. National parliaments have eight weeks to issue reasoned opinions on subsidiarity.
15. Each national parliament has two votes, divided between chambers in bicameral systems.
16. The yellow-card procedure requires review when the relevant threshold of one third of parliamentary votes is reached, subject to the lower threshold for specified justice and security proposals.
17. The orange-card procedure applies under the ordinary legislative procedure when reasoned opinions represent a simple majority of national parliamentary votes.
18. The Court of Justice may review compliance with subsidiarity and proportionality through the procedures established by the Treaties.
19. The intensity of judicial review may vary according to the complexity of the subject matter and the discretion enjoyed by the legislature.
20. The principles are complementary safeguards designed to ensure that European authority is exercised within Treaty limits, at an appropriate level, and through measures that are justified and proportionate.

14. Frequently Asked Questions

1. What is the principle of subsidiarity in EU law?

Subsidiarity is the principle that the European Union should act in areas outside its exclusive competence only where the objectives of the proposed action cannot be sufficiently achieved by Member States acting at national, regional, or local level and can be better achieved at Union level because of the scale or effects of the action.

2. What is the principle of proportionality?

Proportionality requires the content and form of Union action not to exceed what is necessary to achieve the objectives of the Treaties. It prevents Union institutions from imposing unjustified or excessive regulatory burdens and restrictions.

3. Where are subsidiarity and proportionality established?

Both principles are established in Article 5 TEU. Their practical application is further regulated by Protocol No 2 on the Application of the Principles of Subsidiarity and Proportionality.

4. What is the difference between conferral and subsidiarity?

Conferral determines whether the Union possesses the legal competence to act. Subsidiarity determines whether the Union should exercise a non-exclusive competence in a particular situation. A measure must satisfy conferral before subsidiarity can justify the level at which action is taken.

5. Does subsidiarity apply to exclusive EU competences?

No. Article 5(3) TEU expressly limits subsidiarity to areas that do not fall within the Union’s exclusive competence. The principle of proportionality, however, continues to apply to the exercise of Union powers.

6. What is European added value?

European added value refers to the additional effectiveness or benefits that can be achieved through Union action compared with action taken independently by Member States. It may result from cross-border coordination, common standards, reduced regulatory fragmentation, or the management of problems that extend beyond national territories.

7. What is the three-stage proportionality test?

The three stages are suitability, necessity, and proportionality in the strict sense. The measure must be capable of achieving its legitimate objective, must not go further than necessary where an equally effective and less restrictive alternative is available, and must not impose disadvantages excessive in relation to the objective pursued.

8. What is Protocol No 2?

Protocol No 2 is a legally binding protocol attached to the EU Treaties. It establishes procedures for applying subsidiarity and proportionality, including consultation requirements, detailed justification of legislative proposals, national parliamentary scrutiny, and judicial review.

9. What is the early warning mechanism?

It is the procedure through which national parliaments may issue reasoned opinions within eight weeks of receiving a draft legislative act, explaining why they believe it breaches subsidiarity.

10. What is a yellow card in EU law?

A yellow card is triggered when reasoned opinions represent at least one third of the votes allocated to national parliaments. The threshold is one quarter for certain proposals concerning judicial cooperation in criminal matters and police cooperation under Article 76 TFEU. The proposing institution must review the proposal and decide whether to maintain, amend, or withdraw it.

11. What is an orange card?

An orange card applies to proposals under the ordinary legislative procedure when reasoned opinions represent a simple majority of the votes allocated to national parliaments. If the Commission maintains the proposal after review, the European Parliament and Council may prevent further consideration if the specified institutional majorities consider it incompatible with subsidiarity.

12. Can one national parliament block an EU legislative proposal?

No. An individual national parliament can issue a reasoned opinion, but it cannot unilaterally block a proposal through the early warning mechanism. The formal consequences depend on the collective thresholds established by Protocol No 2.

13. Can regional parliaments participate in subsidiarity scrutiny?

Yes. National parliaments may consult regional parliaments with legislative powers when preparing reasoned opinions. This is particularly relevant in Member States with federal or decentralised constitutional structures.

14. Can the Court of Justice annul legislation for violating subsidiarity?

Yes. The Court may review whether legislative acts comply with subsidiarity and may annul an act if it finds that the applicable Treaty requirements have been breached. The legal procedures include actions under Article 263 TFEU.

15. Can proportionality be used to challenge EU regulations?

Yes. An EU regulation may be challenged on proportionality grounds if its provisions are unsuitable, go beyond what is necessary, or impose excessive burdens in relation to the legitimate objective pursued. The assessment depends on the nature of the measure and the relevant standard of judicial review.

16. Does the Court always apply strict proportionality review?

No. The Court recognises that Union institutions may enjoy broad discretion when making complex political, economic, social, or technical assessments. In such areas, judicial review may focus on whether the measure is manifestly inappropriate or otherwise exceeds the limits of lawful discretion. More intensive scrutiny may be required where fundamental rights are seriously affected.

17. What is the relationship between subsidiarity and the duty to state reasons?

The duty to state reasons allows national parliaments, the Union legislature, affected persons, and courts to understand why Union intervention is considered justified. Protocol No 2 requires a detailed statement addressing subsidiarity and proportionality, while Article 296 TFEU establishes the general obligation to state reasons for Union legal acts.

18. Does the existence of cross-border effects automatically justify EU legislation?

No. Cross-border effects may support the argument for Union intervention, but the institutions must still establish that the objectives cannot be sufficiently achieved by Member States and that Union action can achieve them better. The proposed measure must also satisfy proportionality.

19. Are subsidiarity and proportionality relevant only to legislation?

No. Although they are particularly important in legislative decision-making, they also govern other exercises of Union competence. Their application depends on the nature of the Union act and the relevant Treaty provisions.

20. Why are subsidiarity and proportionality important to the constitutional structure of the EU?

They preserve the balance between Union authority and Member State autonomy. Subsidiarity regulates the appropriate level of intervention, while proportionality limits the intensity of that intervention. Together, they help ensure that European integration operates through legally justified and appropriately limited exercises of public power.

Conclusion

Subsidiarity and proportionality occupy a central position in the constitutional structure of the European Union because they address two essential questions concerning the exercise of public authority: where decisions should be made and how far public intervention should extend.

Subsidiarity recognises that the Union is not intended to replace national, regional, and local decision-making wherever a matter has European significance. It requires a justification for intervention at Union level, based on the inability of Member States to achieve the proposed objective sufficiently and the comparative advantages of collective European action.

Proportionality imposes a complementary limitation. Even where Union intervention is justified, the institutions must select measures that are suitable, necessary, and appropriately balanced. The importance of a policy objective does not eliminate the obligation to consider alternative approaches, administrative burdens, financial consequences, and the rights of those affected.

The Treaty of Lisbon strengthened the practical operation of these principles by involving national parliaments more directly in the legislative process. The early warning mechanism allows them to scrutinise proposals before adoption, while the Court of Justice provides a judicial safeguard against unlawful exercises of Union authority.

Their effectiveness nevertheless depends on the quality of the reasoning behind legislative proposals, the availability of reliable evidence, the capacity of national parliaments to conduct meaningful scrutiny, and the willingness of the Court to ensure that institutional discretion remains within legal limits.

The deeper constitutional significance of subsidiarity and proportionality lies in their recognition that the legitimacy of public authority depends not only on the existence of legal power, but also on the justification for exercising it. In the European Union, the question is never simply whether a common rule can be adopted. It is whether the Treaties permit it, whether action at European level is warranted, and whether the measure adopted represents a legally appropriate response to the problem it seeks to solve.

Principal Legal Sources and Further Reading

Treaty provisions

• Treaty on European Union, Article 5 – Conferral, Subsidiarity and Proportionality
• Treaty on European Union, Article 10 – Representative Democracy
• Treaty on European Union, Article 12 – National Parliaments
• Treaty on the Functioning of the European Union, Article 263 – Actions for Annulment
• Treaty on the Functioning of the European Union, Article 267 – Preliminary Rulings
• Treaty on the Functioning of the European Union, Article 288 – Types of EU Legal Acts
• Protocol No 2 – Application of the Principles of Subsidiarity and Proportionality
• Protocol No 1 – Role of National Parliaments in the European Union

Institutional resources

• European Commission – Subsidiarity Control Mechanism
• European Commission – Relations with National Parliaments
• European Parliament – The Principle of Subsidiarity
• EUR-Lex – National Parliaments and EU Decision-Making

Selected case law

• Case C-84/94, United Kingdom v Council
• Case C-233/94, Germany v European Parliament and Council
• Case C-189/01, Jippes and Others
• Case C-58/08, Vodafone and Others
• Case C-547/14, Philip Morris Brands and Others