In this article, the author notes that the principle of non-refoulement has acquired the status of jus cogens, that is, a peremptory norm of international law from which no derogation is permitted. The article briefly examines the origins of the concept and then considers the views expressed by States, particularly in the UNHCR Executive Committee. The author emphasises that the jus cogens nature of non-refoulement is of critical importance today, especially now that the Security Council has begun to adopt resolutions which may have a direct impact on the right of people to leave in search of asylum and not to be sent back to where their lives or freedom may be in danger. The author examines SC Resolution 1373, and considers how the measures required by the Security Council may lead to the return of refugees unless the jus cogens nature of non-refoulement is maintained. The author also examines various measures taken within the European Union, and argues similarly that restrictive policies are likely to be best countered by arguments founded on the peremptory norm of non-refoulement.