For hundreds of years procedural rights such as habeas corpus have been regarded as fundamental in the Anglo-American system of jurisprudence. In contemporary international law, fundamental norms are called jus cogens. Jus cogens norms are rights or rules that can not be derogated even by treaty. In the list that is often given, jus cogens norms include norms against aggression, apartheid, slavery, and genocide. All of the members of this list are substantive rights. In this paper I will argue that some procedural rights, crucial for the fair functioning of criminal proceedings, such as habeas corpus, should also have the status of jus cogens norms. I will begin by explaining what it means for a right to have jus cogens status. And I will follow this with a defense of having procedural rights like habeas corpus added to the list of jus cogens norms. I will then rehearse some of the debates about the jus cogens status of procedural rights in the European Commission on Human Rights. At the end of this paper, I will look at the attempts to deal with the abuses at Guantanamo by the American Commission on Human Rights, and by the US and Australian courts, as a way to understand why there needs to be a stronger support for habeas corpus than is today provided by regional courts.