That would be King Jorge and his neocon buddies. They'll dispense with all this constitution nonsense when the shove the NAU down our throats.
I somehow seriously doubt he came up with this on his own. This is the brainchild of someone in the Justice Department, I suspect. Or maybe State, though less likely. I think it would be extremely interesting to know with whom this idea originated, and why they thought the Mexicans would go along with it.