Since the gubernatorial veto of which you speak is a statutory accommodation and not a constitutional right, the accommodation may be withdrawn by Congress at will. While the circumstances may give rise to a gubernatorial veto, it is still subject to federal approval,  not a matter of right and there is no guaranty of securing agreement of the federal government.

I understand all of that.  I did not say that it was an absolute right.  All I said was that the Court's interpretation of the law as it existed at the time allows state governors to refuse federal deployments if the state can show that such a deployment would compromise the state's emergency readiness.  If memory serves, this was the very case relied upon by the Schwarzenegger administration in refusing deployment of California Guardsmen to the Mexican border in 2006.