Few young European Muslims jump directly into violence: they join gangs, they attend radical mosques, they frequent jihadist chat rooms, and they otherwise flag their presence to the authorities. Security services use the threat of jail, deportation of family members, and so forth to compel their cooperation. This approach works until it doesn’t, that is, until the subjects of scrutiny cease to care about the consequences. As John Schindler observed at the XX Committee blog, there was no “intelligence failure” in Paris: the problem is that the security services are overwhelmed. A pseudonymous European security official made the same point recently at Asia Times Online.

The lesson of Copenhagan is the same as the lesson of Paris: the fragile social peace that European governments have maintained with their Muslim immigrant communities requires a fundamental revision. In the past, European security services let jihadists blow of steam while quietly culling potential killers. That has failed. The alternative is to tighten the screws on Muslim communities.