I’m in the UK so maybe I’m missing something. There’s no point in having a Constitution if it can so readily be discarded, so I think, if the President or any other official is commanding them to do something against the Constitution, they should follow their conscience.
I'm in Australia, safe, maybe missing something like you? What if the President and State Governor issue contradictory orders? What if the Nat. Guard contingent is from a 'Red' State, suppressing protest in a 'Blue' State? What are the consequences of disobeying an order? Define chain of command!