If the President Was or Is Spying For an Enemy, Is That Against the Law?
The sitting President appears to have spied for Russia, which still has nuclear weapons aimed at us, both before his general election and after his inauguration. The subject of the spying appears to have been “Russian oligarchs and their families in US”. I don’t think the Russians were asking him only to read the Manhattan phone book.
By the norms of international law, a head of state is duty-bound to preclude or remove ground for war against the head’s own nation. Where domestic legal provisions would limit that, domestic legal provisions are not law where contrary to the norms. Therefore, in order to preclude or remove ground for war against the head’s own nation, the head may spy on behalf of an enemy nation and may delegate that authority, but generally may not do so where that justification is absent.
Any other person is barred by domestic law from doing such spying unless delegated the relevant authority by the current head of state. I’ve seen no claim that any head of state so delegated the person who subsequently became the head of state; in short, Obama almost certainly did not delegate that authority to candidate Trump.
Thus, President Trump, while President, may not be violating the law by spying on behalf of Russia (whether he violated it depends on the justification per the norms) but he apparently did violate it while a candidate and, if recently enough according to the statute of limitations, can, even now, be criminally liable for spying during his candidacy. While an arrest of a sitting President may be impossible even for a pre-Presidential act, the spying may qualify as an impeachable criminal offense.