Suits against the United States are pretty hard to win, as the government of the United States tries them. Sort of a loaded gun.
And, if they get granted certiorari (doubtful) and lose (which is likely, as the Fed has no power over the states in this matter, and will not move to force Cali to do anything) it could set this whole issue back for at least a decade, if not more.
Be careful what you wish for, you might get it.