the Court understands autonomy to signify that the EU may be a construction of international law, but that in its internal order its own rules displace the principles and mechanisms of international law.
In the Opinion, the Court notes, however, also the principal possibility of the EU and its organs to submit themselves via an international agreement to a binding interpretation of the latter by an external judicial organ (para 182, if not indicated otherwise all paragraph numbers refer to the Opinion of the Court). This principle is nonetheless limited in that the competences of the EU must not be affected in their essential character. In particular, ECHR organs must not be able to bind the EU to a particular interpretation of rules of EU law (paras 183-4).
In the Opinion, the CJEU finds three situations in which an accession of the EU to the ECHR based on the draft agreement could endanger the autonomy of EU law: