He can put them all on the border on a whim if he so desires.
Posse comitatus does NOT apply to the Marines.
Tanks, howitzers, heavy machine guns, helicopters, Warthogs...the media would go nuts and nobody would approach the border.
Have the Warthogs patrol the border at very low altitude at near max cruise speed....have them fly on the Mexican side of the border!
The Warthog at 300ft and 350mph would be a frightful thing. The two huge turbofans would make a sound that would rattle your bones at such low altitude.
The Warthog ain't pretty or fast, it is a scary thing that is sort of like a light tank that flies.
Shut down all trade with Mexico for 30 days if they do not act.
Forbid all remittances to Mexico for a year.
Place the country under martial law if need be and use the entire armed forces at that point.
And get the Corp of Engineers working on the wall...light a fire under their ass.
Have federal marshals arrest all public officials in sanctuary cites.
Trump has the power to do all of these things.
Mess with a genius-level, street-smart, Queens boy and buddy, you got problems.
I don't know about you but I'm pissed, it's time to stop phukin around with this.