All Trump has done is put a timer on this issue. It has never appeared in front of the Supreme Court, so the case law is not settled. He forces the issue with the Executive Order, which obviously will result in immediate lawsuits, which will in all likelihood be appealed over some period of time to the Supreme Court.
It was laying on the floor. He picked it up, dusted it off, and will soon send it out into the world to prove itself or die in the process.
And who knows? Maybe by the time it gets there RBG or another judicial legislator may have moved on too.