France has declared a twelve-day state of emergency. Quoting today's NYT,

France declared a 12-day state of emergency today in an attempt by the government to curb the worst civil disturbances in the country in nearly four decades.
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The law itself states that emergency measures can be enacted by government decree for up to 12 days on all or part of the territory of France. Beyond a curfew, the law gives the authorities powers to conduct raids without a warrant; to restrict freedom of the press and freedom of assembly; to shut down theaters; to close bars; and to put under house arrest any individual whose activities are deemed dangerous to the maintenance of law and order.
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People arrested under the law can be jailed for two months, fined 3,750 Euros, or both.

Why has it come to this? The biggest reason is that France's criminal justice system is broken. Theodore Dalrymple touched on this back in 2002. For more recent evidence, see the above-linked NYT article:

Nearly 400 people have been detained, but few have been jailed; many of the rioters are teenagers, and the vast majority of underage detainees have been released.

To prevent anarchy, a state must jail its criminals. There are two ways to achieve this. One is to forcibly transport criminals to jails. The other is to turn criminals' neighborhoods into jails.

France could do a lot more to try to integrate its immigrants and their offspring; welfare reform especially comes to mind. However, the rule of law is a prerequisite for the success of any such efforts.