Here's how Joe Brandon, the plaintiff's attorney in the Tennessee case, explains opposition to the mosque: "This Shariah-compliant facility must show they are a religious organization, which we vehemently dispute. They are a political organization with Shariah-compliant rules and regulations. Shariah and the U.S. Constitution cannot coexist."
Yes, I know Brandon is an easy target; still, his statement is worth considering. Shariah law is religious law, but because it is the law of a demonized religion associated with terrorism and anti-Americanism, Brandon can label it political, depriving it of First Amendment protections. I don't assume this is a cynical ploy. Blinded by bigotry and their notions of "true" and "false" religions, Islamaphobes may be sincere in the counter-factual belief that Islam is purely political.
That belief is essential to the claim that Shariah law can't be tolerated because it conflicts with the Constitution. Once you acknowledge that Islam is a religion and Shariah law is religious, its conflicts with secular law become arguments for, not against, religious liberty. Of course, Shariah law is inconsistent with the Constitution. So are the tenets of Catholicism, Judaism (especially orthodox Judaism), and most if not all other faiths. Indeed, lawsuits by Catholic institutions challenging health insurance requirements for contraceptive coverage rely on the alleged impossibility of reconciling Catholic articles of faith with secular legal requirements.
Religious and secular laws often conflict; that's precisely why we have a First Amendment. It provides a legal framework for ensuring that religion and government can "co-exist." If religious law were categorically subordinate to the Constitution (as Joe Brandon imagines Shariah law should be), then the Catholic Church would be required to ordain women, Orthodox Jews would have to sit together in shul, and religious groups that oppose gay marriages would be required to perform them.
It's not hard to imagine the uproar that would greet the slightest hint of official interest in violating such basic guarantees of religious liberty, especially if directed against majority or respectable, minority religious practices. It's worth remembering that unpopular religions have long been wrongly denied equal rights: In 1878, the Supreme Court denied Mormons the right to engage in polygamous marriages, which remain illegal today.
But the same principles of liberty that give religious institutions the right not to sanctify gay marriages should also give them the right to sanctify polygamous ones. The same principles that give Christians the right to build churches in Tennessee give Muslims the right to build mosques, just as it gave Mormons the right to build a prominent temple in Belmont, Massachusetts -- a temple opposed by many in town, and a temple that Mitt Romney helped build.