Thanks for the confirmation, Miss Marple. We do have a federal law, the name of which escapes me, which makes it a crime for anyone but duly elected or appointed members of the executive branch to conduct foreign policy. Unfortunately, the law is rarely enforced. In fact, I don't know if it ever has been enforced, but it should be. The Constitution is unambiguous in assigning responsibility for foreign policy to the President.
But there should be a law against inviting a foreign government to interfere in a United States election, although I don't know the US Code.