By Daniela Obradovic
The duty of solidarity between EU Member States
Although the Court of Justice of the European Union (CJEU) long ago characterised the deliberate refusal of a Member State to implement EU law as a ‘failure in the duty of solidarity’ that ‘strikes at the fundamental basis’ of the EU legal order (Case 39/72, para. 25), it has not been clear whether the principle of solidarity among Member States can be enforced in European courts. The recent response of the CJEU to the Slovakian and Hungarian challenge (C-643 and C-647/15, the migrant quotas verdict) to the Council decision on the relocation of migrants from Italy and Greece (the relocation decision) seems to establish that the principle of solidarity between Member States in the area of EU immigration policy can be a source of EU obligations susceptible to judicial enforcement.
The background of the migrant quotas judgment
The exceptional migration flows in 2015 to Italy and Greece prompted the Union institutions to adopt two concrete measures of solidarity with those states. The first measure was enacted on 14th September and the other on 22nd September 2015. They are based on Articles 78 TFEU, which empowers the EU to pass laws benefiting states overwhelmed by a sudden inflow of migrants, and Article 80 TFEU, which stipulates that such decisions must be governed by the principle of solidarity and fair sharing of responsibility between Member States. Those decisions were intended to reinforce internal solidarity in the EU and show the commitment of all EU Member States to share the migration burden with the two Mediterranean countries. (recitals 3-5, 7 and 17 of the decision of 22 September 2015).
The Visegrad group of EU countries (Poland, Hungary, the Czech Republic and Slovakia) have persistently and decisively refused to comply with these relocation decisions. Consequently, Hungary and Slovakia challenged the legality of the relocation decision of 22nd September 2015 before the CJEU. The Court rejected this challenge and upheld enforceability of the duty of solidarity among EU Member States.
The grounds for establishing the duty of solidarity between Member States in EU migration policy
The Court ruled that the contested decision gives effect to the principle of solidarity between EU Member States. It argues that the Council, when adopting the decision in question, was in fact required to give effect to the principle of solidarity between Member States, which applies under Article 80 TFEU when EU migration policy is implemented (paras. 252 and 329 of the Judgment). Because the relocation decision represents a concrete expression of the principle of solidarity, it is capable of imposing the legal obligation of solidarity. Consequently, the duty of solidarity in this domain of EU law is enforceable when it is transformed into a valid, legally binding obligation through the process of the adoption of concrete measures in accordance with a Treaty-based legislative procedure.
Advocate General (AG) Bot, who gave the Opinion in this case, also submits that the principle of solidarity between Member States in the area of EU immigration policy has a specific content and a binding nature (para. 23 of the Opinion). In his view, the principle laid down in Article 80 TFEU is transformed into a valid, legally enforceable obligation through the process of the enactment by the Council of concrete measures such as the relocation decisions (para. 22 of the Opinion).
Definition of solidarity in EU migration policy
Although the Court does not provide a fully-fledged definition of the principle of solidarity between EU Member States, it identifies some elements thereof. According to the Court, this principle imposes a legal obligation upon EU Member States to act for the benefit of other Member States even when such actions are not in their own interest (para. 291 of the Judgment). This finding echoes its previous pronouncement that a state cannot breach EU rules for the sake of the protection of its own conception of national interest (Case 39/72, para. 24). The Court expressly recognised that the application of this principle leads to the establishment of a clear distinction between beneficiaries of policies and the rest of the Member States, which should accept the responsibility of sharing the burden carried by the beneficiaries even if that sharing is not compatible with their national interests (para. 293 of the Judgment).
However, the Court failed to determine the distinction between the principle of solidarity and the principle of loyalty. The determination of the demarcation line between these two principles is crucial for clarifying the precise content of the solidarity principle in EU law. This is so because, in its previous case law, the Court often refers to the duty of solidarity in the context of the application of the loyalty clause stipulated in Article 4(3) TEU (see e.g. Joined Cases 6/69 and 11/69, para. 16).
The CJEU’s assessment of the content of the solidarity concept in the area of EU migration policy differs quite substantially from the pretty ambiguous elaboration of this notion in the Slovak Council Presidency Report on this matter. In that document, the application of the principle of solidarity between EU Member States in the immigration domain is made conditional upon the responsibility of the beneficiaries of this principle to undertake all possible measures in order to reduce their burden, which should be shared with other states conforming with the duty of solidarity (p. 3 of the Report). By contrast, the Court does not subject the triggering of the duty of solidarity among Member States in EU migration matters to such a condition.
Compulsory nature of solidarity commitments in EU migration policy
Furthermore, in its ruling the CJEU rejected the view that the application of the principle of solidarity between EU Member States is based upon voluntarism. In its application concerning the case at hand, Slovakia stipulates that the Member States’ commitments under EU migration policy should be executed ‘in a spirit of solidarity’ which it considers to be ‘less prejudicial’ to state sovereignty than the duty of solidarity governing the application of the contested EU relocation decision (para. 231 of the Judgment). Slovakia argues that solidarity is not a legally binding principle but merely a non-compulsory source of policy inspiration.
This interpretation of the role of solidarity in EU migration policy was adopted in the 2001 Temporary Protection Directive (TPD). It was enacted in order ‘to contribute to the attainment of a balance of effort between Member States in receiving and bearing the consequences of receiving displaced persons in the event of a mass influx’ (Preamble, recital 5). The TPD includes a mechanism to pursue solidarity among Member States, via financial support and physical relocation based on the principle of volunteerism. It does not introduce a mandatory relocation mechanism, but stipulates in Article 25 that Member States should receive migrants in ‘a spirit of Community solidarity’ on a voluntary basis. This directive has never been activated. No reference to it can be found in the relocation decisions.
While the concept of ‘the spirit of solidarity’ implies that this notion cannot be codified in legal terms, the Court’s ruling regards solidarity as a category which can impose legally binding effects, provided that it is concretized through specific measures taken in accordance with a legislative procedure. It implicitly rejects the opinion that the principle of solidarity among Member States should be a basis for voluntary commitments. Furthermore, the voluntary character of the TPD solidarity mechanism has been brought into doubt. In the Study on the TPD commissioned by the Commission, it is warned that there is a risk of violation of Article 80 TFEU if the TPD’s solidarity mechanism and other EU acts do not contain appropriate measures to give effect to the principle of solidarity and fair sharing of responsibility (pp. 68 and 69).
Enforcing values in the EU
The position of Slovakia emanates from the proposition that solidarity is a value and not a general principle of EU law. Although, in the judgment in question, the CJEU does not discuss the very nature of the duty of solidarity in EU migration policy, AG Bot in his Opinion on the case regards this concept as an EU value irrespective of the fact that it is omitted from the list of the EU values presented in Article 2 TEU (paras. 18-19 of the Opinion). Solidarity is referred to as a core element of the cooperation between EU Member States in the Schuman declaration of 9 May 1950, which represents the founding act of the EU. According to Article 3(3) TEU, the EU aims at promoting ‘economic, social and territorial cohesion, and solidarity among Member States’. The Charter of Fundamental Rights of the EU in its Preamble also identifies solidarity as a value upon which the Union is founded.
In principle, values as such should not be imposed by coercive means upon those who do not embrace them. Consequently, for values to be properly enforced, that is, to be coercively imposed upon somebody who does not agree with them voluntarily, they should first be transformed into law according to the rules which govern the legislative process. Value-laden provisions of EU law could be enforceable in courts through legally binding instruments which represent the expression or emanation thereof. It seems, based on the Court’s findings presented above, that this approach to enforcement of the principle of solidarity between EU Member States is accepted in EU immigration policy.
Enforcement of solidarity among Member States in other areas of EU law
The CJEU has already recognised the existence of the duty of solidarity between EU Member States in the area of free movement of persons. It claims that a certain degree of financial solidarity between Member States is inherent in all EU instruments relating to the rights of free movement and residence. This duty of solidarity between Member States in the area of free movement of persons becomes a legally enforceable rule because the legislative act which governs this section of EU law, Directive 2004/38, is a specific expression thereof.
However, the CJEU does not find that all solidarity clauses embedded in the Treaty provisions give rise to legally enforceable obligations. For example, it asserts in Pringle (para. 135) that the solidarity principle enshrined in Article 122(1) TFEU does not establish the duty of solidarity among Member States in respect to sharing of financial responsibilities arising in the context of the European Monetary Union (EMU). AG Kokott in her opinion in this case (para. 143) claims that it cannot be inferred from the concept of solidarity that there exists a duty upon EU states to provide financial assistance to the members experiencing budgetary difficulties. This is at odds with the Court’s migrant quotas judgment which specifies that the solidarity principle laid down in Article 80 TFEU, which includes financial solidarity, can become legally enforceable after being concretised through legislative measures. Furthermore, while in Pringle (para. 142s) the CJEU pointed out that the application of the EMU-based principle of solidarity is conditional upon the fulfilment of a series of obligations, no such requirement is imposed upon unleashing solidarity obligations in the area of EU migration policy.
The Court’s inconsistency in the interpretation of the legal effect of various solidarity clauses incorporated in the EU Treaties originated in its preposition that this principle can be a source of legally enforceable obligations only when concrete legislative measures operationalise its application. The general and abstract character of this principle necessarily entails that the margin of discretion that the European legislator enjoys when putting the principle into effect, through the enactment of secondary law, is wide. Consequently, what solidarity effectively means depends, to a large extent, on the specific circumstances of the sector in which it shall apply. The enforceability capacity of different EU solidarity clauses is contingent upon the nature of the concrete social-economic settings prevailing in a particular EU policy. A EU immigration policy based on solidarity and fairness is not only a normative requirement enshrined in the Treaties, but also a functional necessity arising from the general objective of a single market without internal frontiers, one in which the free movement of person is realised. This is so because once internal borders between EU Member States are removed, the decision of migrants to enter the EU becomes a common concern to all Member States.
Value-laden concepts, such as the principle of solidarity between EU Member States, are unlikely to produce legally binding commitments on their own. They can be enforceable in courts only when they are transformed into concrete hard law provisions adopted in accordance with a legislative procedure. This position was embraced by the CJEU when it decided in the migrant quotas case that the duty of solidarity between EU Member States represents a source of their legally enforceable obligations. However, it is debatable under which conditions the solidarity clauses in specific areas of EU law can be put into effect. The CJEU does not provide precise and mutually consistent guidelines on the matter. It seems that the exact effect of the solidarity principle among Member States depends upon the concrete circumstances existing in the sector in which the principle will apply.
 Some scholars claim that solidarity in EU migration policy should be interpreted restrictively in the sense that it is closely connected to the reciprocity and conditionality principle. See e.g. Peter Hilpold, ‘Understanding Solidarity within EU Law: An Analysis of the ‘Islands of Solidarity’ with Particular Regard to Monetary Union’ (2015) 34 Yearbook of European Law 257.
 Giulio Itzcovich, ‘On the Legal Enforcement of Values. The Importance of the Institutional Context’ in Andras Jakab and Dimitry Kochenov (eds) The Enforcement of EU Law and Values (OUP 2017) 28 at 29.
 C‑140/12 Brey, para. 72; C‑184/99 Grzelczyk para. 44. See also Opinion of AG Sharpston of 4 September 2014 in C‑359/13 Martens, para. 79; Opinion of AG Wahl of 20 March 2014 in C 255/13 I, para. 57 .
 Economic, social and territorial cohesion (Art. 3(3) TEU); external action (Arts. 21, 24(2)(3), 31, and 32 TEU); immigration policy (Arts. 67(2) and 80 TFEU); energy policy (Arts. 122 and 194 TFEU); terrorist attacks (Art. 222 TFEU); natural or man-made disasters (Arts. 122 and 222 TFEU); and balance of payments assistance (Art. 143 TFEU).
 See also Opinion of AG Cruz Villalón of 14 January 2015 in C‑62/14 Gauweiler, para. 131 and Peter Hilpold, ‘Understanding Solidarity within EU Law: An Analysis of the ‘Islands of Solidarity’ with Particular Regard to Monetary Union’ (2015) 34 Yearbook of European Law 257.
 Esin Kucuk, ‘The Principle of Solidarity and Fairness in Sharing Responsibilities: More than Window Dressing?’ (2016) 22 European Law Journal 448 at 449.