Enlargement fatigue is over. While the last country to join the EU was Croatia over one decade ago, the topic is once again high on the political agenda, with Montenegro’s accession treaty currently being drafted and Albania closing its first chapters. Russia’s full-scale invasion of Ukraine has fundamentally transformed the enlargement approach. While the main objective of stabilising and democratising neighbouring countries has always been accompanied by geopolitical considerations, the new wave of enlargement centres around these time-sensitive concerns. This creates a difficult tension. Geopolitical concerns, particularly the expansion of Russian influence in the Western Balkans, suggest a fast and large-scale process, while accession requires far-reaching reforms that are difficult to achieve quickly. The Commission continues to insist that the process must remain “strict, fair and merit-based”. As a result, a range of proposals has emerged, aiming to balance timely accession with EU values and its institutions. While some aspects of prominent concepts have already found their way into EU policy, others go further, including proposals to temporarily restrict new members’ veto rights in sensitive areas such as the Common Foreign and Security Policy. These are increasingly relevant in the context of the drafting of Montenegro’s accession treaty. With it constituting the first treaty drafted in this new wave of enlargement, it is expected to set a precedent for following treaties.

This raises fundamental questions: Is the EU currently engineering an accession treaty that tackles problems at their root, or are post-accession safeguards externalizing the Union’s own institutional weaknesses? What implications could this bear for the credibility of the broader accession process?

Mapping the approaches

A plethora of concepts have been put forward by think tanks and political figures. One in particular has influenced Brussels and beyond: the Staged Accession Model proposed by the European Policy Centre Belgrade and the Centre for European Policy Studies in 2021 and revised in 2023. It introduces measures to make enlargement more gradual, credible and rewarding before full accession, and tackles the concerns that an enlarged Union might become dysfunctional if its institutional design remains unchanged.

Some of its ideas have since found their way into EU legislation, such as the conditional financial incentives incorporated in the Growth Plan. Of particular importance for the current debate, however, are the proposed extended post-accession safeguards, which apply to the period after accession, once a country has closed all chapters of the acquis and gained membership. Such safeguards are currently being considered in the drafting of Montenegro’s accession treaty and are expected to go further in both scope and duration than previous examples, such as those included in the 2005 Accession Treaty with Bulgaria and Romania, which largely focused on specific areas like the internal market. But one of the Model’s proposals, the temporary limitation of new members’ veto powers, remains particularly controversial. The proposal has increasingly entered the political debate, particularly regarding the Common Foreign and Security Policy (CFSP). While safeguards have seen many precedents, a veto limitation would constitute the first of its kind and is argued to touch directly on the equality of member states, risking a “second tier” membership. Montenegro, for its part, has stressed that stronger safeguards may be acceptable, but that restricting voting rights would cross a red line.

The rationale behind these proposals is understandable. Against the backdrop of a growing security threat and the internal tensions of the past years, avoiding a democratically backsliding and CFSP-blocking “Hungary 2.0,” is high on the agenda. Including extended post-accession safeguards and a veto limitation thus appear as attractive quick-fix measures. But are these adjustments tackling the issues at their root or are they simply externalising the Union’s institutional shortcomings?

The EU’s shortcomings: On the Copenhagen dilemma

The Union has already enshrined sanctioning mechanisms for breaches of its fundamental values in both its treaties and secondary legislation, that post-accession safeguards and the veto limitation are now proposed to tackle.

Most prominently, this includes Article 7 TEU, the Union’s “nuclear option,” intended to protect the EU’s founding values under Article 2 TEU. It encompasses both a preventive mechanism for a clear risk of breach and a sanctions stage that can ultimately lead to the suspension of a member state’s rights, including its voting rights. Yet no procedure has ever reached the latter.

Much can be said about the Article’s limitations. The procedure is slow, highly political and subject to demanding voting thresholds. In the European Council, the preventive stage requires a four-fifths majority, while the sanctions stage requires unanimity, excluding the member state concerned. The possibility of member states protecting one another through cross-vetoes has made this threshold particularly difficult to overcome. In the past, Poland and Hungary even preemptively publicly pledged to veto sanctions against the other. The result is a mechanism that depends purely on political will to initiate, responds with delay and faces unrealistic thresholds.

Consequently, other ways of responding to rule-of-law backsliding and breaches of EU values have been developed, most notably through financial conditionality. The 2020 Rule of Law Conditionality Regulation allows the Union to suspend or reduce funding where breaches of the rule of law affect, or risk affecting, the EU’s financial interests. It has therefore added a material dimension to the Union’s enforcement toolbox. But its scope remains limited. The EU can only withhold or suspend funds if a rule-of-law breach directly affects the financial management of the EU budget. While it has shown effect, general democratic backsliding or civil rights violations not exhibiting a direct nexus with the budget cannot be penalised under this specific tool and sanctions regarding political rights cannot be imposed either.

The shortcomings of these main tools expose the Copenhagen dilemma. The EU can enforce compliance with its rules and standards through conditionality during the accession process, but has considerably weaker mechanisms to enforce those same values once membership has been obtained. It is precisely this gap that stronger post-accession safeguards seek to address.

But the gap is not unique to future members. While some new members have shown democratic backsliding, the issue neither exclusively applies to them, nor does it appear in a determined timeframe after accession. Once any additional safeguard expires, the Union is still left with the same, insufficient enforcement architecture. If the EU wants an enlarged Union upholding common values sustainably, it needs mechanisms capable of enforcing them against all member states at any point after accession.

The EU’s shortcomings: On Veto powers

The most controversial proposal touches upon the veto power of new member states. Unanimity in the Council constitutes a prerequisite in the decision-making process in numerous policy areas, but Russia’s full-scale invasion of Ukraine has shifted CFSP-vetoes into the centre of the debate. With Europe’s ambition to respond collectively and swiftly to security threats, the ability of one member state to block common action has become a considerable vulnerability.

Hungary has illustrated this. Former President Viktor Orbán repeatedly obstructed or significantly delayed recent CFSP decisions through a veto, including, the mobilisation of European Peace Facility funds for military assistance in Ukraine. The result has been repeated delays and efforts to work around a member state that effectively paralysed the Union’s ability to act decisively.

The concern about reproducing this problem in an enlarged Union and an increasingly tense geopolitical environment is thus straight forward. However, the issue does not lay within future member states using a veto but in the very institutional framework that allows for one member state to block swift and collective action in the first place. A temporary veto suspension for new member states, would thus, again, only externalise the underlying issue temporarily.

What distinguishes the veto proposal from the extended safeguards, however, is its nature. A safeguard responds to a violation of previously agreed-on standards, while a veto restriction changes the rights attached to membership itself. A country would have completed the accession process expecting to gain full membership, only to then be withheld an essential right of it. Montenegro’s position illustrates this distinction. Willing to accept safeguard-clauses, it has stressed that no second tier of membership should be created, naming the veto restriction as a red line.

The credibility problem

This matters beyond the immediate question of the aforementioned institutional efficiency. Externalising the Union’s institutional weaknesses onto future members comes with another cost: credibility. A core principle of enlargement is conditionality. It entails that candidate countries receive concrete rewards for their compliance with standards, while being withheld benefits when failing to comply, thus constituting a “carrot-and-stick” approach. If this does not hold anymore, it likely negatively affects the incentive of aspiring member states to comply. The External Incentives Model (EMI) conceptualises this logic of incentive. Governments are incentivised to undertake reforms to comply with standards when the expected rewards of compliance outweigh the domestic political and economic costs. In the EU’s case, the prospect of equal membership constitutes the ultimate reward.

Needless to say, an incentive does not constitute a guarantor. Where the domestic costs of compliance are particularly high, governments may have little interest in reform. This can be particularly pronounced where public support for EU membership is weak, as in Serbia, or where ruling authorities pursue other interests, such as regime survival, as recent developments in Georgia illustrate.

Nevertheless, for the candidates willing and able to undertake reform in principle, the credibility of the conditionality promise matters. During the accession process, the EU’s conditionality is backed by a credible “stick”: benefits can, and have been, withheld when candidates fail to meet conditions. Current proposals are, however, challenging the “carrot.” If candidates undertake costly reforms on the understanding that fulfilling previously agreed-on conditions will lead to equal membership, but are then offered a “second tier” membership, this could create a credibility deficit, not only for the country concerned, but for other aspiring members too. The issue thus goes beyond whether post-accession safeguards, such as veto restrictions, are effective or appear as “fair.” They could signal to candidate countries that fulfilling conditions does not necessarily guarantee the rights associated with full membership.

This has a geopolitical dimension.

The EU seeks to increase European security through enlargement, but the success of this ambition depends on the credibility of its offer. If the EU demands compliance with an increasingly elaborate accession process, while making the rewards of membership after compliance less certain, it risks weakening the very attractiveness on which its transformative power depends. In a neighbourhood where other actors can offer fewer conditions for more immediate rewards, it should be in the EU’s interest to not undermine the credibility that makes its enlargement policy effective.

An honest look inwards

Enlargement begins at home. The credibility of the membership offer ultimately depends on the Union being willing to address the weaknesses that make additional safeguards attractive in the first place. Stronger and transitional safeguards can help manage genuine risks, but they should not become a substitute for reform. Neither the lack of sanctioning mechanisms nor the complications created by veto powers are problems that enlargement itself creates, but weaknesses of the Union that enlargement exposes. Externalising these shortcomings solely through post-accession safeguards is short-sighted and might harm the EU’s broader enlargement ambitions.

The current geopolitical momentum around enlargement could instead be used as an opportunity for a more honest debate about both sides of the process: not only where candidate countries are expected to deliver, but also where the Union needs to address its own weaknesses. This should include a genuine look inwards at what kind of institutional architecture would allow an enlarged Union to function effectively and sustainably. It should furthermore not be limited to addressing sanctioning mechanisms or changing the treaties. Prominent proposals also point towards ways of working within the existing framework. These include a 2023 European Parliament resolution calling for greater use of the Treaty’s passerelle clause, while scholars point to moving substantive decisions outside the CFSP. Rather sooner than later, however, the foundational questions must be addressed.

The candidate countries are doing their homework. It is time for the member states to do theirs.