It is also possible for Parliament to create statutes that conflict with public international law. In Cheney v Conn [1968] 1 All ER 779, a taxpayer challenged the validity of the Finance Act 1964. He argued that it conflicted with the Geneva Convention, a treaty to which the UK was a party, because part of the tax collected would go to the manufacture of nuclear weapons.

Ungoed-Thomas J said: 'What the statute itself enacts cannot be unlawful, because … it is the highest form of law known to this country. It is the law which prevails over every other form of law, and it is not for the court to say that a Parliamentary enactment… is illegal.'