Agreed, the Supreme Court should be held accountable for its rulings.
My question is this - in your hypothetical, how could the two state governors be held accountable for their actions? Your logic seems to dictate that as soon as the governors declared an invasion, it would become treason to take any action against their declaration.
And? Are not things in law substantiated on two [or more] witnesses?
I worry far less about abuse by governors [ATM] than I do about the feral FedGov; the way to beat governors is to act like, and demand that, the State's Constitution means what it says.
I've looked at all the States's Constitutions where I would be living, only this one have I given less than a good read-through... I only skimmed it. (Though that reminds me that I should give it a better read.)