'Je suis Charlie' - the defiant cry in a clash of values

Two sides in conflict over whether there should be limits to the liberty of self expression clashed in an usually tranquil side street on the Right Bank of Paris.

When it was over, a dozen people were dead - including some of the most prominent political cartoonists and satirists in France, and the police officers assigned to protect them.

Wednesday's attack at the offices of the magazine Charlie Hebdo seems to be the latest chapter in a clash of values between the West and a version of militant Islam that is at least a quarter of a century old, beginning when Ayatollah Khomeini, Iran's supreme leader, issued a 1989 fatwa calling for the assassination of novelist Salman Rushdie, accused by some conservative Muslims of blasphemy.

In France, the conflict over what limits to place on press freedom has often involved the satirical weekly, whose mix of crude - often obscene - artwork and brashness has few if any parallels in Anglo-Saxon media.

Press freedom and the right to self-expression in general differs vastly in the world, with even a generally liberal country like Sweden passing laws that criminalise hate speech and prohibiting expressions of contempt directed against a group or one of its members.

Depending on the political system or climate, critiquing the ruler or the government may be a red line few dare to cross - treated as taboo, criminal or even treasonous. In extreme cases, some governments have sought to extend their bans on criticism outside their own borders, attacking dissidents abroad, or using diplomatic means to quell insults or demand respect.