[Poohbah]

Not quite. The land was willingly ceded by Russia in 1867 - at that point it's in the possession of the U.S., regardless of what happened to Russia in 1917.

True enough, but the end of a regime doesn't automatically invalidate any agreements, otherwise territorial cessions WOULD turn into these sorts of nasty international legal messes.

[Senator Pardek]

...otherwise territorial cessions WOULD turn into these sorts of nasty international legal messes.

I disagree. The 1967 Alaska Treaty no longer exists. Czarist Russia must reform, invalidate the treaty, and invade.

I would not label that under "international legal mess" but "quite ludicrous and causing no problems".