Um, I realize the Trump administration doesn't pay a lot of attention to what it does and does not have authority to do, but I'm having trouble imagining what they'd even claim their authority was...

All they have to do is say "national security" again and then they're in the clear (in their minds, at least).

Ever see the old Twilight Zone episode with the 6-year-old kid who wishes you into the cornfield if you don't do what he says?

https://en.wikipedia.org/wiki/It%27s_a_Good_Life_(The_Twilig...

That's his authority.