@freemo well for anyone else who's interested in this line of thought, I'd emphasize no *legal* check.
There are bureaucratic checks, folks in the chain of command who can put up speedbumps or be hassles to any command, whether it be "bring be coffee" or "launch a nuke".
It's not about legality at that point but about management of the sprawling executive branch of the US government.
At some point it might be easier to fulfill some legal requirement than to get cooperation out of some 18 year old service member five levels down a management bureaucracy..