The offices of the French satirical weekly Charlie Hebdo are petrol-bombed the day the magazine releases its own ironic tribute to the Arab Spring with a special "sharia" issue. It is, of course, no coincidence. But the fact that such a violent act is taking place in secular France, which has the biggest Muslim and Jewish communities in the EU, is an unexpected and worrying development.

Charlie Hebdo, a kind of Gallic Private Eye, stronger on cartoons than words, is no stranger to controversy. In 2006, out of solidarity with the Danish publication Jyllands-Posten, attacked by Islamist fundamentalists, it reprinted the now famous 12 cartoons representing the Prophet Mohamed, along with its own series lampooning other religious figures. Sales skyrocketed, and the issue became a collectors' item overnight. Its cover showed Prophet Mohamed with his head in his hands, crying and lamenting: "Oh, how hard it is to be loved by imbeciles!"

After the publication of the Danish drawings fuelled massive protests in the Muslim world during which 50 people died, the question of reprinting those drawings, in the name of freedom of expression, was raised in many European countries. Only Britain stood out. Urged by the Blair government, no British publication dared provoke fundamentalists' anger. Traumatised perhaps by the London bombings which took place only a few months earlier, the British press lay low. Charlie Hebdo didn't. It was sued for its trouble, but it won. "Criticism is no racism," said Philippe Val, the magazine's editor at the time.

Surveys have showed that the six million French Muslims and 600,000 French Jews are the most integrated in Europe. An overwhelming majority feel first and foremost French; they embrace the Republic's idea that religion belongs to the private sphere. However, the past 20 years have also seen religious practices increase in those communities. In 1989, 60 per cent of French Muslims said they observed Ramadan. This year, the figure was 70 per cent.

Last week, many French commentators were baffled that the 600,000 Franco-Tunisians who took part in Tunisia's elections voted en masse for the Islamist party, Ennahda. This seemed a surprising choice, especially in the light of party chairman Rached Ghannouchi's diatribe against the "Franco-Arab linguistic pollution".

This week's Charlie Hebdo's special "sharia issue" is precisely pointing out the irony in the so-called Arab Spring. Campaign for equality and get polygamy! Fight for democracy and wake up with sharia law! Here is a fertile subject for satirists. The "terrorist attack" against Charlie Hebdo, as the French Interior Minister immediately called it, should bolster the sales of its sharia issue. Hopefully, it will instil some much needed humour and resistance spirit to a disturbing trend, as well.