Jus cogens or “cogent law” is a set of principles generally deemed so important in international law that individual nations cannot pass laws that would derogate or suspend these principles. Also known as a peremptory norm, it integrates input from numerous nations on compelling legal issues deemed important for social order, as well as human rights. Nations that attempt to pass laws in violation of jus cogens can be subject to challenge and penalties.
A classic example is slavery. By international agreement, slavery has been deemed illegal and harmful to human society as a whole. The slave trade is banned under international law. Individual countries cannot pass laws permitting slavery or activities connected to the slave trade, including the use of slaves as laborers. These laws would derogate international antislavery principles. While restrictions on the legal systems of individual nations are usually considered violations of sovereignty, issues like slavery are considered so unilaterally unacceptable that bans on laws permitting slavery are allowed.
Other topics covered under jus cogens include genocide and torture. These human rights abuses are banned by international law and, as with slavery, nations cannot pass laws that may create legal allowances for these activities. This has proved to be a bone of contention with torture, as nations have disputed whether certain types of interrogation methods can legally be considered torture. Some nations have authorized the commission of activities like waterboarding on the grounds that they are not torture, and thus permitting them does not violate just cogens.
International courts exist for trying people suspected of convicting violations of international law. Organizations like the United Nations can be involved in censuring leaders and nations who participate in the passage of laws and authorizations that might undermine jus cogens. In organizations like the European Union, member nations also have the option of challenging each other in the Union's high court on the grounds that they are passing laws antithetical to the function of the EU. as well as the international community.
Legal scholars have engaged in brisk historical debate over the scope and detail of jus cogens. The goal is to strike a balance between interfering with the legal rights of individual nations to protect themselves and pass laws in the interests of their citizens, and allowing nations to engage in activities that appear to be clear violations of basic principles of decency and humanity. The basic precepts of international law are considered so sacrosanct that they cannot be abridged or infringed by individual nations.