Well, if they found no reason to stop Obama from enacting the EO in the first place, they saw nothing unconstitutional in it. (Also may have been an issue of legal standing). In this instance, in reversing it a judge found the reversal to be unconstitutional / capricious.
I agree with you that this is not statute by law...my point in my post was exactly that - it doesn't have to be for courts to determine its constitutionality.
This is one of those cases.
when you say capricious you are giving the judiciary the right to strike down laws that it believes is not necessary. They should not have that power. If you give them the other 2 branches are nearly worthless.
also keep in mind you are giving this power to a judiciary that will be stacked with conservatives. Trump doesnt give a shit about the judiciary and is perfectly willing to let the federalist society select all the nominees.