"Peremptory norms" are fundamental rules or principles that must be followed by everyone, without any exception. They are non-negotiable and cannot be ignored. Think of them as basic standards that everyone must adhere to. Full definition
To the author's knowledge, the Committee's report appears to be the only Greek authoritative statement defining peremptory norms within the context of restorative justice and mass atrocity law. (opiniojuris.org)
[61] Jus cogens or peremptory norms of international law are overriding principles of international law, distinguished by their indelibility and non-derogability. (humanrights.gov.au)
How does the last principle sit with regards to the right to self determination, which seems to be getting closer to becoming a peremptory norm? (politics.stackexchange.com)