Above Every Treaty
Jus cogens: the highest tier of international law
Most international law works through consent. Countries negotiate treaties, sign them, ratify them, and thereby agree to be bound by them. The system is voluntary by design. But there is a small body of law that works differently. These norms are so fundamental that no State can opt out, no treaty can override them, and no government can claim exemption. This small body of law is called jus cogens, from the Latin for “compelling law.”
Jus cogens sits at the top of the international legal hierarchy. Its defining characteristic is that it cannot be derogated from. If two countries sign a treaty that violates a jus cogens norm – such as agreeing to jointly engage in the slave trade – that treaty is void. Not voidable. Void. The norm overrides the agreement regardless of what the parties consented to.
In 2022, the International Law Commission published a non-exhaustive list of recognized jus cogens norms. The list includes eight rules:
the prohibition of aggression,
the prohibition of genocide,
the prohibition of crimes against humanity,
the basic rules of international humanitarian law,
the prohibition of racial discrimination and apartheid,
the prohibition of slavery,
the prohibition of torture, and
and the right to self-determination.
These are the eight rules that are binding on every State in the world, whether it likes it or not.
The list is not fixed. Last year, the Inter-American Court of Human Rights issued an advisory opinion stating that the obligation not to cause irreversible damage to the climate and the global environment constitutes a jus cogens norm – the first time any international court has made such a finding. Three of the Court’s judges, including its president, dissented from this conclusion. But the reasoning is significant: the Court held that dangerous human-driven interference with the climate system constitutes an existential threat demanding a universal response, and that conduct causing irreversible damage to the ecosystems that sustain life is strictly prohibited. If that reasoning is accepted universally, it would place climate destruction in the same legal category as genocide and slavery.
The challenge is jus cogens runs into the same wall as most of international law: enforcement. Torture is a jus cogens prohibition, yet torture still occurs regularly. There is no international police force nor any automatic sanction for violating jus cogens.
What jus cogens does accomplish is to place certain acts beyond legal justification. A State cannot argue that it was allowed to commit genocide, or that a bilateral agreement authorized slavery. It also means that all States – not just a directly affected party – can demand compliance when a jus cogens norm is breached.