I mean, the EU doesn't have unlimited authority. The US federal government doesn't either. Imagine if someone claimed some law didn't fall into interstate commerce, that would be similar.

Here the regulation is based on Article 122, clause 1 TFEU, which reads: "Without prejudice to any other procedures provided for in the Treaties, the Council, on a proposal from the Commission, may decide, in a spirit of solidarity between Member States, upon the measures appropriate to the economic situation, in particular if severe difficulties arise in the supply of certain products, notably in the area of energy."

Exxon argues the windfall tax isn't appropriate to remedy any shortage