ISTANBUL Iran on Monday vowed a “proportionate and appropriate response” if European signatories of the 2015 nuclear deal reinstated UN sanctions under the so-called snapback mechanism. At a press conference in Tehran, Foreign Ministry spokesman Esmaeil Baqaei criticized recent threats by Britain, France, and Germany to activate the “snapback” mechanism, which could reimpose sanctions on Iran under UN Security Council Resolution 2231. Baqaei described the European position as “a political act