Peremptory norms in play

Lawyers and diplomats are using one of international law’s highest rules — jus cogens, or peremptory norms — to argue some trade and maritime measures can be unlawful even when a state calls them domestic enforcement. (legal.un.org) Jus cogens means a rule no state can contract around or legislate away. Article 53 of the Vienna Convention on the Law of Treaties says any treaty that conflicts with a peremptory norm is void, and the International Law Commission adopted draft conclusions on those norms in 2022. (legal.un.org) The International Law Commission’s annex gives a non-exhaustive list of examples: the prohibitions of aggression, genocide, crimes against humanity, racial discrimination and apartheid, slavery, and torture, plus the basic rules of humanitarian law and the right of self-determination. (legal.un.org) That matters in 2026 because the legal fight is no longer limited to treaties. Recent commentary is trying to connect those non-derogable rules to shipping access, arms cargoes, import bans, sanctions, and tariff-style enforcement measures that states describe as ordinary regulation. (opiniojuris.org) At sea, the baseline rules still come from the United Nations Convention on the Law of the Sea. It gives foreign ships a right of innocent passage through the territorial sea, lets coastal states suspend that passage only temporarily and without discrimination in specified areas for security reasons, and bars coastal states from hampering passage except as the convention allows. (un.org) That is why recent legal arguments have focused on whether a vessel’s cargo can make its passage non-innocent, or whether a coastal state may have to act when a ship is allegedly linked to conduct that would aid breaches of peremptory norms. A 2024 expert opinion circulated by advocates argued coastal and flag states must stop vessels carrying military supplies that assist serious violations, while other scholars have said the law of the sea does not clearly support such an expansion. (bdsmovement.net) (sciencedirect.com) On the trade side, the same move appears in arguments about coercive agreements and import restrictions. A January 2026 analysis on Opinio Juris said Article 53 is a weak fit for many unequal trade deals because the current jus cogens catalogue is narrow, but it still treated peremptory norms as a live constraint where trade terms are tied to coercion, force, or denial of self-determination. (opiniojuris.org) Governments, meanwhile, are expanding domestic trade enforcement on other legal theories. The Office of the United States Trade Representative says it uses trade agreements, dispute settlement, and U.S. trade laws for enforcement, and U.S. Customs and Border Protection says it is enforcing forced-labor import bans under Section 307 and the Uyghur Forced Labor Prevention Act. (ustr.gov) (cbp.gov) In March 2026, the Office of the United States Trade Representative opened Section 301 investigations into whether 60 economies failed to establish or effectively enforce forced-labor import prohibitions. The Federal Register notice called forced labor an economic and national security issue and asked whether foreign practices burden or restrict U.S. commerce. (ustr.gov) The split in these debates is over how far the hierarchy of norms reaches. One camp says peremptory norms can override conflicting treaty terms and shape duties of non-recognition and non-assistance; the other says using jus cogens to justify broader boarding, blocking, or trade retaliation risks stretching a narrow doctrine into a general foreign-policy tool. (advisorycommitteeinternationallaw.nl) (ejiltalk.org) For now, the doctrine’s core is settled and its edge cases are not. The rule no state may breach is clear; whether that rule can invalidate a tariff, stop a ship, or compel a port denial in a current dispute is where the legal fight is moving. (legal.un.org)