Charles Krauthammer believes that Trump is within his rights to restrict travel, but he pointed out that Trump should let the travel moratorium go and focus on vetting and the other aspects of his agenda:
I do believe that the president is completely within his rights in issuing an order that is lawful and legal. Under normal circumstances, I think he’d be vindicated by the Supreme Court. I think Judge Napolitano may be right, that there will be at least one liberal on the court who will support him because I think it is pretty obvious, and it would embarrassing if the liberals on the court all unanimously opposed it. But as a pure political, tactical issue, I do think that you can let this thing go. There are two parts. There’s the vetting, and there’s the moratorium. The moratorium is incidental and temporary. You let that go, you go back to the district court, it’s dragged out — the moratorium would expire anyway in 90 days — you do the vetting, you get Giuliani or somebody else to put together a program and have it done within the 90 days, and then you move on.
I think it is a matter of personal pride. The guy’s a winner. He doesn’t like losing, but I think it’s a losing proposition to run after this, unless you think you can win with the supremes. You may or may not, if you want too roll the dice, but otherwise, let it go, escape from it, you’re not getting anywhere on this, you’ve got a huge agenda, you’re on a roll — don’t mess it up.