Valid legal basis: The Constitution is the Supreme Law of the Land (US Const., Art. VI, Cl 2) and Sharia law is patently unconstitutional.
The Constitution is rightly called a "social contract," as incorporated by "We the People of the United States." Islam works directly to supplant the Constitution and violate the protections of inalienable rights of citizens, particularly to inhibit their 14th Amendment right to equal treatment under the law their 1st Amendment free exercise of religion. Hence, anyone who prays five times a day to Allah, is not a participant in that social contract and is therefore undue of its protections.
Muslims cannot, will not and decline to assimilate to our Constitution. Koran states to kill the INFIDEL.