Jindal's claim was particularly brazen because it came just a day after Fox News apologized for a comment an alleged expert made on air. Steve Emerson, who analyzes terrorism for the network, said on Fox News Sunday, "There are actual cities like Birmingham that are totally Muslim, where non-Muslims just simply don’t go in." British Prime Minister David Cameron ripped Emerson as only an old Etonian can: "When I heard this, frankly, I choked on my porridge and I thought it must be April Fools' Day. This guy’s clearly a complete idiot." Emerson apologized, but other Fox personalities repeated variations on the theme, and eventually Fox issued on-air corrections on both Fox & Friends and Justice With Judge Jeanne.

Fox isn't known for shying away from controversial claims, so the decision to move so aggressively to reverse is an indicator of how wrong the claim is. Of course, that came after several days of Fox personalities repeating the claim casually on air. (The retraction didn't come in time for one group, apparently: Paris' mayor said Tuesday that Paris would sue Fox News for sullying its image.)

But where did the claim come from in the first place? Like many political myths, there's a partial basis in fact that has become exaggerated into a hyperbolic and, in this case, inflammatory and dangerous claim.

It seems to stem from two or maybe three real phenomena. The first is the presence of sharia courts in some places in Europe. In the United Kingdom, for example, "Muslim Arbitration Tribunals" are officially mandated but set up outside the court system and can resolve civil and family issues through Islamic law; there are also reports of informal religious courts. There are similar Jewish courts in Britain, and the Muslim tribunals have received encouragement from figures including then-Archbishop of Canterbury Rowan Williams. On the other hand, there are convincing arguments that the courts can sometimes be bad for women. (There's a fascinating echo of the Ottoman empire's "millet" system, in which non-Muslims were allowed to set up their own courts to deal with matters of personal law.)

The second real phenomena is the rise of vigilante sharia squads in some places. For example, in Whitechapel, East London, CNN reported on bands of Muslim men who try to keep alcohol out of the area and harangue passers-by about morality. RedState's Erick Erickson thinks he's caught CNN red-handed: While the network criticizes Jindal for not knowing of any real no-go zones, CNN itself reported on one! But the analogy doesn't quite hold. What's happening here is disturbing, but well-short of extremist-run enclaves. These are just ad-hoc groups, and area Muslims by and large condemn it in CNN's reporting. There's no evidence that these squads are powerful or widespread.