In Britain, a counter-extremism task force is working on a plan to encourage imams to preach in English, the Telegraph reported last month. The report noted that the plan arose “amid concern that preaching in foreign languages enforces divisions between Islam and mainstream British society and can foster radicalization.” It cited a senior government source who said, “If imams are speaking in another language it makes it far harder to know if radicalization is taking place.”

In France, this rationale has been offered up by far-right National Front party leader Marine Le Pen, who claimed in 2014 that, “It’s not difficult to require sermons in France to be given in French. That would also make it much easier to report what subjects are being dealt with.” Le Pen is not the only French politician to call for this requirement; it gained support from across the political spectrum after the 2015 Paris attacks. Another French politician put it bluntly: “Sermons in France shouldn’t be in Arabic.”

Considering that fundamentalist recruiters don’t need to speak in Arabic to be extremely successful at what they do, it’s not clear how clamping down on Arabic-language sermons would represent a viable counterterrorism strategy. After all, Anwar al-Awlaki, the al-Qaeda propagandist and cleric, gave many recorded sermons in English. In the U.K., prominent preachers like Anjem Choudary, Abu Hamza al-Masri, and Omar Bakri Muhammad likewise delivered their messages in English before they were convicted for supporting terrorism.

“It’s easy to preach a resistance message even when you’re speaking the same language as the people you’re preaching against,” said Brenna Powell, a Stanford scholar who studies civil conflict. “And even when they speak the same language, people are often very good at manufacturing code.”

Although preaching in Arabic makes it harder for those who don’t speak the language to “decode” the substance of the message, that doesn’t mean an Arabic sermon is more likely to be radicalizing anyone. It could just be more likely to make non-Muslim Europeans nervous about what’s going on in mosques.

But experts say that’s not where most Muslims who adopt extremist views are getting them.

“We can’t just pin everything on mosques,” said Mubaraz Ahmed, an analyst with the Centre on Religion and Geopolitics who specializes in jihadi groups and online extremism. “Overwhelmingly there’s an acceptance within the [countering violent extremism] field that radicalization doesn’t take place in mosques; it’s increasingly taking place elsewhere. Certainly in the ISIS era, a lot of it is online, with encrypted messaging services”—like WhatsApp and Telegram—“coming under the spotlight.”

Scott Atran, an anthropologist who studies terrorism through fieldwork with Islamic fundamentalists and others, echoed this statement. “Traditional religious education is a negative predictor of involvement in these movements,” he said in an email, adding that most who join jihadi movements from Europe are young adults who are “born again” into extremist strains of Islam, and that a significant number are converts (more than one in four in France, for example).