30While, in the absence of relevant EU rules, the detailed rules for implementing such provisions are a matter for the domestic legal order of the Member States, under the principle of their procedural autonomy, they must not, however, be less favourable than those governing similar domestic situations (principle of equivalence) or render impossible in practice or excessively difficult the exercise of rights conferred by EU law (principle of effectiveness) (judgment of 26 November 2014, Mascolo and Others, C‑22/13, C‑61/13 to C‑63/13 and C‑418/13, EU:C:2014:2401, paragraph 78 and the case-law cited).
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