[oldasrocks]

Why can’t Trump fire or reassign some of these Federal judges?

[Regulator]

Because a President can’t do that. Only Congress can impeach judges.

And they damn sure should.

[Buckeye McFrog]

Why can’t Trump fire or reassign some of these Federal judges?

A little thing called the US Constitution. POTUS has no authority over Federal Judges.

Congress however can impeach them. Or use their authority granted by the Constitution to assign the jurisdiction of inferior courts (reduce the 9th. Circuit to a five-block jurisdiction around the Presidio, and restrict Federal Courts from hearing immigration cases), or the size of SCOTUS (expand it to 13 justices and pack with Conservatives).