The Logan Act of 1799 was written for just this purpose. (18 U.S.C.A. § 953 [1948]) is a single federal statute making it a crime for a citizen to confer with foreign governments against the interests of the United States. Specifically, it prohibits citizens from negotiating with other nations on behalf of the United States without authorization. The Boston Globe reports that he is working against the Trump Administration to save Obama’s Iran Deal.
The United States does not need John Kerry’s possibly illegal Shadow Diplomacy on the very badly negotiated Iran Deal. He was the one that created this MESS in the first place!
— Donald J. Trump (@realDonaldTrump) May 7, 2018