Abstract This analysis explores in detail various aspects of the possible legal impact of ‘British’ Protocol No 30 (the so‐called opt‐out from the EU Charter of Fundamental Rights). On the basis of a legal appraisal,
it concludes that the Protocol is not in any way to be understood as a substantial derogation from the standard of protection of fundamental rights in the EU or as an ‘opt‐out’ from the Charter in a substantial sense. Nevertheless, its significance is definitely not to be
underestimated. Its adoption as a source of primary law enshrines a legally binding interpretation of the Charter and, in particular, an interpretation of its horizontal provisions. In Article 1(2) and Article 2, the Protocol in fact confirms that the application of the Charter cannot lead
to a change in the existing competencies framework. These provisions are of a declaratory nature and apply to all Member States. In Article 1(1), the Protocol is of a constitutive nature since it rules out an extensive interpretation of what can be considered national legal acts adopted in
the implementation of EU law only for those States signed up to the Protocol. This specifically means that if, in the future, as part of the application of the Charter, the Court of Justice of the EU (ECJ) has a tendency to subsume a certain area of national legislation under the ‘implementation
of Union law’ outside the field of implementing standards, in the spirit of the Ellinki Radiophonia Tileorassi judgment (and subsequently allow their reviewability with respect to their conformity with the Charter), such action would be admissible only for those Member States that have
not acceded to the Protocol. However, the Protocol cannot exclude the continued application of the general principles of law instead of the positively constituted fundamental rights in the Charter by the ECJ.