The letter said the missiles were "inherently capable of delivering nuclear weapons". However, it stopped short of saying the tests were illegal. Resolution 2231 calls for Iran to refrain from activity related to nuclear-capable missiles ("Iran is called upon not to undertake any activity related to ballistic missiles designed to be capable of delivering nuclear weapons, including launches using such ballistic missile technology"[3]), but according to unnamed diplomats in a Deutsche Welle report, the language is not legally binding and cannot be enforced with punitive measures.[4]