It has been noted that "developments in international law since 1945, notably the United Nations (UN) Charter, including its prohibition on the threat or use of force in international relations, may well have made the declaration of war redundant as a formal international legal instrument." In addition to this, non-state or terrorist organisations may claim to or be described as "declaring war" when engaging in violent acts. These declarations may have no legal standing in themselves, but may still act as a call to arms for supporters of these organisations.