Paris yesterday: all copies of the post-mortem Charlie Hebdo issue with the Prophet on the front, a tear in his eye, rapidly sold out. In our local backwater in the south-west, I’d already driven to the nearest newsagent. There, too, sold out. ‘They should have sent us 150 copies,’ the man on the till explained, ‘but we only got 11.’ Then came news of a massive new run, bringing the total number of copies to five million, with deliveries to retail outlets spread over several days. But this morning it was the same story: every copy gone by eight in the morning, though this time the local shop only received six. Tomorrow for sure.

France is now at war, apparently. The prime minister, Manuel Valls, announced it – not for the first time – on Tuesday. He was speaking at the National Assembly, after a minute’s silence and a chorus of the ‘Marseillaise’ from the deputies. War against anyone in particular? No. Valls proposes to pursue ‘terrorism, jihadism and radical Islamism’ while avoiding any collateral damage against ‘Islam and Muslims’. The plan is to beef up the security services, cull more inquisitive data on airline passengers, carry out closer internet and social media surveillance, isolate living quarters for radical jihadists in jail, and counter a ‘new anti-semitism’ founded on hatred of ‘the state of Israel’. The prime minister wants to ‘protect’ French Muslims, and come down hard on offenders desecrating mosques and cemeteries. Muslims, meanwhile, should have their own ‘debate’ with a view to stamping out ‘conservatism and obscurantism’.

Valls hit all the right buttons; there were tears in the chamber, there was thunderous applause, and the following morning the controversial comedian and actor Dieudonné – an incontinent anti-semite – was arrested on suspicion of condoning terrorism. He’d proclaimed on his Facebook page that he felt a bit of a ‘Charlie Coulibaly’, a provocative reference to the hostage-taking and murder of four Jewish customers in the kosher supermarket in Porte de Vincennes.

At the time of writing there are roughly 40 cases, like Dieudonné’s, of ‘apologie du terrorisme’, an offence with harsh consequences since a change in the law last year. There will not be a French version of the Patriot Act, but ‘freedom of expression’ is under scrutiny. And it will now be even harder than it was a week ago to speak up against Israel’s occupation of the West Bank, or another onslaught in Gaza, without being accused of anti-semitism.

What did Dieudonné mean by ‘Charlie Coulibaly’? It’s opaque but I think it goes something like this: ‘Charlie Hebdo did enviably well as transgressors, and doubtless you think they’d gone to the limit by putting their lives on the line, but now watch this: I, Dieudonné, am ready to identify with Amedy Coulibaly, the kosher killer, so screw you and your hypocritical Republican values, and screw the staff at Charlie Hebdo for trumping my high-density brand of anti-semitism with their hand-me-down Islamophobia.’ (Despite a major row in 2008 CH has, by and large, steered clear of Jew-baiting.)

So Dieudonné exercised a right to freedom of expression before the remark was removed, even if he may have infringed the law against condoning terrorism. But what is it with all this sounding off? Does the right to freedom of expression need to be exercised with monotonous regularity? Is it really the case that every moment we refrain from airing an opinion or firing off an insult, we undermine a bulwark of democracy, or a key Republican value? These are good questions for Dieudonné.

They’re also questions for CH, even though it’s obvious that Charb and his colleagues were never going to back down. Theirs was a militant libertarian view of freedom of expression, informed by a tough Republican antipathy to ‘cults’ and clergy, a strong identification with the left and maybe even a dash of Anglo-Saxon atheist radical chic. A lot of things the magazine has run are very funny but not much of it is harmless fun. French culture understands the power of the sign. Paris built much of its (dwindling) reputation as an intellectual centre on a prolific study of ‘discourse’: during the heyday of structuralism and its long, creative decay, language and representation were teeming sites of intellectual labour, so it isn’t as if cartoonists reach for their pencils like angels reaching for their harps.

And there’s more than freedom of expression at stake if you decide to depict Muslim women at prayer with their buttocks exposed; or ridicule the Prophet; or commend the Dutch cartoonist Gregorius Nekschot, collaborator of Theo van Gogh, for his drawings, which run from Islamophobic sexual insults to crass generic defamation (an idle Arab on a cushion announcing that ‘the Koran doesn’t say we have to do anything to draw 30 years of unemployment and social benefits’). Don’t we worry that somewhere in all this, the racial stereotype is looming, even if it’s operating behind the shield of secularism, an honourable Republican tradition? That’s how Olivier Cyran, a journalist of German origin, who broke away from the paper in 2001, came to think of it. In 2013 he published an open letter to Charlie Hebdo’s editors in Article 11, setting out his criticisms with a measured fury. The piece, which resurfaced recently in Mediapart, now carries a postscript that advises anyone who believes it was an a priori justification of the Charlie Hebdo murders to get stuffed.