Non-Muslims are barred from entering the cities of Mecca and Medina — not merely barred from building synagogues or churches, but barred, period, because their infidel feet are deemed unfit to touch the ground. This is not an al-Qaeda principle. Nor is it an “Islamist” principle. It is Islam, pure and simple.

“Truly the pagans are unclean,” instructs the Koran’s Sura 9:28, “so let them not . . . approach the Sacred Mosque.” This injunction — and there are plenty of similar ones in Islam’s scriptures — is enforced vigorously not by jihadist terrorists but by the Saudi government. And it is enforced not because of some eccentric sense of Saudi nationalism. The only law of Saudi Arabia is sharia, the law of Islam.

As Sunni scholarly commentary in the version of the Koran officially produced by the Saudi government explains, only Muslims are sufficiently “strict in cleanliness, as well as in purity of mind and heart, so that their word can be relied upon.” Thus, only they may enter the holy cities. Authoritative Shiite teaching is even more bracing. As Iraq’s “moderate” Ayatollah Ali Sistani — probably the world’s most influential Shiite cleric — has explained, the touching of non-Muslims is discouraged, because they are considered to be in the same “unclean” category as “urine, feces, semen, dead bodies, blood, dogs, pigs, alcoholic liquors, and the sweat of an animal who persistently eats [unclean things].”

These teachings are worth bearing in mind as we listen to the staunch defenses of religious liberty that have suddenly become so fashionable among proponents of the Cordoba Initiative, a planned $100 million Islamic center and mosque to be built on the hallowed ground where remains of the nearly 3,000 Americans killed by Muslim terrorists on 9/11 >prohibits these infidels from polluting the kingdom with their Bibles, crucifixes, and Stars of David.

Mosque proponents like the Manhattan Institute’s Josh Barro >infamous for its support of Hezbollah. Recently, four Christian missionaries were arrested by Dearborn police for the crime of handing out copies of St. John’s gospel on a public street outside an Arab festival. The police called it disturbing the peace. But the peace was disturbed only due to the foreboding sense that Muslims might take riotous offense, because sharia forbids the preaching of religions other than Islam.

In Minneapolis, where thousands of Somalis have settled, taxpayers are being forced to support sharia-compliant mortgages and at least one Islamic charter school. Meantime, taxi drivers refuse to ferry passengers suspected of carrying alcohol, and a student in need of a dog’s assistance for medical reasons was driven from school due to threats from Muslim students against him and the animal — because sharia regards canines as unclean.

This aggression is a deliberate strategy, called “voluntary apartheid.” The idea, as explained by influential Sunni cleric Yusuf Qaradawi (the Muslim Brotherhood’s spiritual guide), counsels that Muslims in the West must push political leaders to indulge what he claims is their “right to live according to our faith — ideologically, legislatively, and ethically.” It is what imam Feisal Rauf means when he urges America to become more sharia-friendly by allowing “religious communities more leeway to judge among themselves, according to their laws.”

This is not the promotion of religious liberty. In America, President Obama observed, religious liberty welcomes “people of all faiths.” Contemporary Islam, by contrast, is counseling supremacism. It rips at our seams, demanding that Americans accept parallel Islamic societies, because Muslims must reject the mores of non-Islamic societies.

This same thinking undergirds Islam’s rejection of freedom of conscience, including the Koran’s prescription, in Sura 4:89, of the death penalty for those who renounce their Islamic faith (“They would have you disbelieve as they themselves have disbelieved, so that you may be all like alike. Do not befriend them. . . . If they desert you seize them and put them to death wherever you find them.”) Again, this is not an al-Qaeda doctrine. As the scholar Ibn Warraq >The Grand Jihad: How Islam and the Left Sabotage America.