48Thus, in the judgment of 15 July 1964, Costa (6/64, EU:C:1964:66, pp. 593 to 594), the Court found that the establishment by the EEC Treaty of the Community’s own legal system, accepted by the Member States on a basis of reciprocity, means, as a corollary, that they cannot accord precedence to a unilateral and subsequent measure over that legal system or rely on rules of national law of any kind against the law stemming from the EEC Treaty, without depriving the latter law of its character as Community law and without the legal basis of the Community itself being called into question. In addition, the Court emphasised that the executive force of Community law cannot vary from one Member State to another in deference to subsequent domestic laws, without jeopardising the attainment of the objectives of the EEC Treaty or giving rise to discrimination on grounds of nationality prohibited by that treaty (judgment of 21 December 2021, Euro Box Promotion and Others, C‑357/19, C‑379/19, C‑547/19, C‑811/19 and C‑840/19, EU:C:2021:1034, paragraph 246).
Source: EUR-Lex, © European Union, 1998-2026. Reuse authorised under Decision 2011/833/EU.