And there already have been two arrests. The Telegraph:

Two Muslim women wearing full face veils have been arrested within hours of France's burka ban becoming a law, as they were taking part in a demonstration against the new measure in front of Notre Dame Cathedral in central Paris.

Technically, the women should now face fines of 150 euros (£133), as well as citizenship lessons, but officers involved in the arrest said they were likely to be released "shortly' after being questioned about an "illegal gathering."

"They should not be here demonstrating against anything, least of all the face veil ban," said one officer, who was wearing full riot gear as he stood outside Notre Dame.

"Women officers will be dealing with the offenders, and the matter will be dealt with as sensitively as possible."

Alexis Marsan, a public order official who also attended the scene, confirmed that the rally in front of the cathedral was unauthorised, and that others taking part had also been arrested.

Rachid Nekkaz, a Muslim activist who organised the demonstration, said the rally had been called to protest the ban, which is the first of its kind to be enforced in Europe.

What the ban says about France and the assimilation of Muslims is simple: we will accommodate your religious beliefs only as far as they do not conflict with western values. That's a fine attitude to have - especially if Europe is to maintain any kind of western identity.