As a constitutional principle embodied in Article VI of the U.S. Constitution, supremacy instructs the judicial department to uphold federal law and ignore conflicting state law. Likewise, though primacy of EU law was not expressly recognised in the EC Treaty (now replaced by the Treaty on the Functioning of the European Union (TFEU), which is also silent in this respect) this circumstance did not prevent the European Court of Justice (ECJ) from introducing this principle into the newly created EU legal order. Not only has primacy been interpreted, along with direct effect, as the foundational constitutional principle, but primacy has also become a legal basis bestowing national courts with all necessary powers to set aside conflicting national laws. It follows from the foregoing that both the EU and the U.S. legal orders mandate the judicial department to ensure that infringing states do not contest that federal law is "the supreme law of the land." To this effect, there is an essential linkage between this principle and the constitutional law of remedies. The perspective adopted to characterise this linkage will determine how much remedial power must be granted to the judiciary for it to accomplish its constitutionally assigned mission. On the one hand, one may argue that supremacy is only ensured where there is a judicial remedy for every violation of a federal right. Thus, compliance with the maxim ubi jus, ibi remedium conditions the supremacy of federal law. Said differently, failure to provide an adequate remedy erodes the supremacy of federal law. On the other hand, one may consider that even if there is not always an available remedy for every violation of a federal right, the supremacy of federal law is ensured in so far as states remain bound by the rule of federal law. Allowing a certain degree of infringement does not deprive federal law of its supremacy. Rather, it gives equal importance to other constitutionally protected interests, such as the role played by states in the federal design, which may advise against granting judicial relief. Put simply, supremacy of federal law cannot be construed as an absolute remedial grant, but its supreme character is apprehended by weighing it against other constitutional principles.
J. A/ Gutierrez-Fons, Comparing Supremacy: Sovereign Immunity of States in the United States and Non-Contractual State Liability in the European Union, 28 Penn St. Int'l L. Rev. 199 (2009).