There are those on this forum that will insist that deploying the NG for such duty violates the Posse Comitatus Act, but they're either ignorant or lying. (If the former, hopefully they learned their lesson yesterday).
Border enforcement is currently defined as a LAW ENFORCEMENT mission, and a federalized National Guard is a MILITARY entity.
Congress would have to give explicit approval for the mission.
And, if you got your way...you would have succeeded in crippling thew ability of the US Army to project power overseas. There are many foreign countries and terrorist organizations who would be willing to pay a LOT of money to bring that about, good sir.