As of March 2019, two states have not yet ratified Protocol 15 ECHR. When that Protocol enters into force, the Convention’s Preamble will be amended and a reference to the margin of appreciation and subsidiarity will be included therein. It is well-known that notions of subsidiarity and deference have generated substantial attention over the last years; the question of the legitimacy of the Strasbourg Court has emerged as a widely debated topic. The Copenhagen Declaration (April 2018) serves as further evidence of this claim. This paper will argue that i) Protocol 15 will have implications for the Convention system; ii) albeit not in the direction that some critics of the Strasbourg Court might have anticipated, since it will leave the ECtHR in a relatively strong position despite the amendments in the Preamble; iii) yet it will also incite the Court to provide clearer definitions on the margin of appreciation, as well as on its relationship with European consensus.