Interestingly, according to the Politico article, apparently DOD has plenty of appropriated money that can be redirected to “respond to requests by local law enforcement agencies.” So, for example, if Texas and Arizona requested DOD to build a wall, the President could apparently direct that those funds, already appropriated, toward wall construction.
That's a no brainer. My feeling here is that Pelosi saying NO, will backfire on the Dems beyond belief. It forces Trump to "work for" getting the wall started and for that, vs. being easy and compromising and allow Dems to take credit, he's doing it on his own. He will benefit politically beyond imagination. He's like Superman, building the wall against ALL odds. People will give him 110% credit now - huge.
A new wrinkle in wall funding.