What is the law, is a question people ask for which there frequently is no clear answer. The Supreme Court allowed the Trump travel.
More accurately, 5 judges allowed the law, while 4 suggested it be struck down. And several lower courts found it invalid. See Washington v Trump, 847 F.3d 1151 (9th Cir. 2017).
The decision illustrates several principles,
- Different courts can see the same law in different ways,
- Facts can be emphasized in varying ways, and one can look at the various opinions to see how each judge emphasized different facts.
- Judges have predilections like everyone else, and that can influence their decisions.
Rather than asking what is the law which supposes a clarity and certainly that usually does not exist, ask what are the factor that courts will consider and how will they be weighed.