SCOTUS has already ruled 9-0 that the president has the right to exclude aliens. So he can't lose on that.
No, they didn't.
As you quoted:
and the Executive’s authority to do so, are undoubtedly at their peak when there is no tie between the foreign national and the United States.viating obvious hardship to anyone else...
That doesn't say he has an absolute right to do so. It says the authority is at its "peak" - it's strongest. It doesn't exclude the possibility that such an order might be invalid in some circumstances. It's important to differentiate between authority and a right in this case. Authority can be withdrawn far easier than can a right.
I don't think anyone (sane) believes that he doesn't have the authority to exclude aliens, or that doing so to those with no ties to the US would have the least restrictions, but the question that arises is the definition of a tie. As the SCotUS also said it's a question of injury to the rights of others that comes into play and again, that's why it's key not to call the Executive's authority a right. The rights of others cannot be abridged by virtue of an authority that does not carry the same level of right (i.e. constitutional).
If Trump's smart (and he's not, but sometimes he know when to leave well enough alone such as the law suits he dropped before taking office), he'll do the review, tighten up the checks, and then move on and hope the SCotUS decides there's no longer anything to decide (because if they decide and limit his authority, then it's done - testing things in court that can go against you when you really don't have anything to gain is silly).
Again, I don't think anyone feels that more robust or thorough checks on people coming from potentially dangerous regions is a problem. The problem is that he didn't include the place all the 9/11 terrorists came from (instead he sold them billions of dollars in arms), and the language and scope of his order was inept. Had he been more reasonable and sensible, he could have easily worked on increasing the vetting and implementing stronger restrictions and actually achieved something, instead of attempting to grandstand and show who was boss and falling flat on his face.
