On 27 June 2023, Iran sued Canada in the International Court of Justice, alleging that the exception for state supporters of terrorism in Canada’s State Immunity Act violates customary international law. This article argues that Canada’s terrorism exception is consistent with customary international law. Although it is commonly assumed that state-supported terrorism is acta jure imperii and that a general and consistent practice of states accompanied by opinio juris is required to create an exception to state immunity, in fact, neither assumption is correct.