The main reason they may not have pursued this option - the Office of the President of the United States has the power to nationalize the National Guard troops of any state, for a “national emergency”.
Even if a valid national does not exist or is acknowledged at the moment, wouldn’t take too long to invent one....
The final outcome is entirely up to the governors.
Baraq Hussein can command, the governors can refuse.
How many states is Baraq Hussein willing to send his army against to enforce an illegal unconstitutional order?
How many soldiers will be willing to obey the illegal order?
They all take an oath to defend and protect the Constitution of the United States against ALL enemies, foreign and DOMESTIC!