D.G. Myers is right that French authorities bungled badly in the affair of Mohamed Merah who was on a terrorist watch list but was allowed to roam freely. That terrible mistake was obviated somewhat by the swift and massive French response after the terrible shootings at the Jewish day school; Merah was identified and cornered within two days of that attack and stopped before he could kill again.
But whatever the French did wrong in this case — and there is no doubt that a terrible oversight occurred — on the whole French counter-terrorism is a success story. I recommend reading this 2008 article by Reuel Marc Gerecht and Gary Schmitt that calls France “the European country most serious about counterterrorism.” The secret of French success has been their willingness “to grant highly intrusive powers to their internal security service, the Direction de la Surveillance du Territoire (DST), and to their counterterrorist, investigative magistrates, the juges d’instruction” — powers that far exceed any authorities given U.S. government officials even under the Patriot Act. With those powers, French forces have done an impressive job of stopping terrorist plots of which there is no shortage because of the large number of marginalized and aggrieved Muslim immigrants living there. Indeed France’s real mistake is not doing more to assimilate Muslims which ensures a constant supply of plotters; the blame is more on society and government as a whole than on the security forces which are on the whole quite effective.
The Toulouse tragedy merely goes to show that any system, no matter how vigilant, cannot prevent all terrorist attacks. As the saying has it, the security forces have to be right all the time; the terrorists have to be right only once. The real test now for the French authorities will be how they conduct their “lessons learned” exercises and what they do to patch the holes uncovered by Mohamed Merah.