Not if you are working against the interests of the USA.
So you cannot be a a contractor on policy and draft up policy that is against the interests of the USA, and.... continue to be a citizen of the USA? Hired on as a campaign manager of a candidate?
What standard are you using for this? As far as I know only have official policy about having business deals with Iran, I know of nothing with Russia.
I accept what fski said about his failure to disclose and lying about his connection to Russia, obviously we need better than that. But the fact that he was hired by a Russian aluminum magnate is not the problem.