50However, according to the case-law of the Court, the Member States must exercise their powers in compliance with EU law and they cannot therefore, in so doing, undermine the effectiveness of Directive 2009/72 (see, by analogy, judgments of 30 June 2005, Candolin and Others, C‑537/03, EU:C:2005:417, paragraphs 25 to 27, and of 17 December 2015, Szemerey, C‑330/14, EU:C:2015:826, paragraph 42).