31It 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).
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