He doesn't have this power, but he declared a "national emergency" and put out an edict.

Legislators are supposed to review this and revoke it (and impeach him for abuse of powers), but Republicans are capitulating, ergo nothing can be done until someone with standing sues and it reaches the Supreme Court.

Then we have to assume they will rule it is unconstitutional, despite half of them being installed by him, and that he will listen to them.