How about prohibiting entry based on forbidden practices of a religion. Like suicide bombing and beheading and polygamy ? The government has interfered with other religions based on ILLEGAL practices.
You don’t ban as a religion. You ban based on the home where the person is coming from, i.e., Syria, Iraq, Jordan, etc. Just as in WW II, we did not accept any Japanese immigrants. Except for a few scientists whom we captured in 1945, I don’t think we accepted any German or Italian immigrants after 1941.