Kingdom of Spain v European Parliament and Council of the European Union.
Date: 2015-09-08
18. Furthermore, to accept as lawful the establishment of an ad hoc participation procedure would render Article 4 of the Schengen Protocol ineffective, since a Member State which was refused permission to take part in the adoption of a measure developing the Schengen acquis  would, notwithstanding that refusal, be able to participate in the measure by means of that ad hoc procedure. That system would therefore be incompatible with the law as stated by the Court in its judgments in United Kingdom  v Council  (C‑77/05, EU:C:2007:803) and United Kingdom  v Council  (C‑137/05, EU:C:2007:805).
27. Since Ireland and the United Kingdom do not take part in all the provisions of the Schengen acquis , they are in a special situation, which the Schengen Protocol took into account in two respects (see, to that effect, judgment in United Kingdom  v Council , C‑77/05, EU:C:2007:803, paragraph 57).
28. First, Article 4 of the protocol reserves to those two Member States the right to apply at any time to take part in all or some of the provisions of the Schengen acquis  in force on the date of the application to take part. Secondly, Article 5 of the protocol, which governs the adoption of proposals and initiatives to build upon the Schengen acquis , allows those Member States to choose whether or not to take part in the adoption of such a measure, with that option being available to one of those Member States only if the context of the measure is an area of the Schengen acquis  which that Member State has accepted pursuant to Article 4 of the protocol, or if the measure is a development of such an area (see, to that effect, judgments in United Kingdom  v Council , C‑77/05, EU:C:2007:803, paragraphs 58, 62 and 65, and United Kingdom  v Council , C‑482/08, EU:C:2010:631, paragraph 61).
31. It follows that the EU legislature cannot validly establish a procedure that differs from that provided for in Article 4 of the Schengen Protocol, whether in the direction of strengthening or easing that procedure, for the purpose of authorising Ireland or the United Kingdom to take part in such provisions or in the adoption of such proposals and initiatives (see, to that effect, judgment in Parliament  v Council , C‑133/06, EU:C:2008:257, paragraph 56).
44. On this point, it should be recalled that, according to settled case-law of the Court, when interpreting a provision of EU law account must be taken of its wording, its context and its aims (see, to that effect, judgments in United Kingdom  v Council , C‑77/05, EU:C:2007:803, paragraph 55, and van der Helder and Farrington , C‑321/12, EU:C:2013:648, paragraph 36).
51. In the first place, it follows from the general scheme of the Schengen Protocol, from Declaration No 45 on Article 4 of the Protocol integrating the Schengen acquis  into the framework of the European Union, and from the principle of sincere cooperation that the system established in Articles 4 and 5 of the Schengen Protocol cannot be regarded as intended to require Ireland and the United Kingdom to participate in the entire Schengen acquis , excluding any form of limited cooperation with those Member States (see, to that effect, judgment in United Kingdom  v Council , C‑77/05, EU:C:2007:803, paragraph 66).
53. Similarly, the fact that the Member States participating in the Schengen acquis  are not obliged, when they develop and deepen the enhanced cooperation which they have been authorised to establish by Article 1 of the Schengen Protocol, to provide for special adaptation measures for the other Member States (judgment in United Kingdom  v Council , C‑482/08, EU:C:2010:631, paragraph 49) does not mean that the EU legislature is prohibited from enacting such measures, in particular allowing certain limited forms of cooperation with those other Member States, where it finds it appropriate.