His argument is not that they have rights, rather that it is tantamount to establishing a religion in reverse. That is, it “unfairly” rejects one religion over all others. I’m sure the courts would agree, right or wrong.
As a strategy, Trump would have to somehow define Islam as a political movement, which, or course, it is. But that will be unlikely, according to the definitions of religion that exist.
It’s a system of governance, a supra-nation defined by religious ideology, at war with the west. He could ask Congress for a moratorium and SCOTUS would not touch it.
Trump’s lawyers already, I am sure, have it mapped.