A more thorough explanation:

Jus cogens, also known as peremptory norm, refers to fundamental principles of international law that are considered to be overriding and non-derogable.

According to Article 53 of the Vienna Convention on the Law of Treaties, a treaty is considered void if it conflicts with a peremptory norm of general international law.

Examples of jus cogens norms include prohibitions against crimes against humanity, genocide, and human trafficking. These norms are considered to be fundamental and non-negotiable, and are recognized by the international community as such.

For instance, the prohibition against genocide is a jus cogens norm that is recognized by the international community as a fundamental principle of international law. This norm prohibits the intentional destruction of a national, ethnic, racial, or religious group, and is considered to be a non-derogable norm that cannot be violated under any circumstances.