More details emerged after the arrests. Halimi had been held in several different places in and around Bagneux, whose residents, most of them immigrants, did not appear to have noticed anything out of the ordinary. Such densely populated immigrant areas are considered "no-go areas" ("zones de non droit") where the police cannot operate freely .
It's been this way for a while.
Last year, I was reading a story about drug smuggling on the French border.
The muslims have a system where they send a "rabbit" car crashing through border gates, triggering a pursuit. With the border gate security lessened, they then crash a tractor trailer full of drugs through the same gate.
The police will pursue the vehicles right up to the edge of the muslim-controlled "no go" slum housing, then they stop the pursuit. It gets too dangerous for law enforcement at that point. Once the muslim smugglers reach "home base" they are untouchable and can unload their cargo at their leisure.