18 U.S. Code § 953 - Private correspondence with foreign governments:

Any citizen of the United States, wherever he may be, who, without authority of the United States, directly or indirectly commences or carries on any correspondence or intercourse with any foreign government or any officer or agent thereof, with intent to influence the measures or conduct of any foreign government or of any officer or agent thereof, in relation to any disputes or controversies with the United States, or to defeat the measures of the United States, shall be fined under this title or imprisoned not more than three years, or both.

I am willing to bet that someone in the Ukrainian foreign ministry was aware of this law, and then had some pointed questions for the US State Department on whether or not Elon’s refusal to share intelligence should be taken as an official US position on the matter, and if not, why Elon/SpaceX’s behavior is effectively contradicting official US policy.

This should get interesting, and it could put Elon in some real legal jeopardy on a matter that the US tends to not fuck around with.