The recent disappearance and assumed killing of 43 Mexican students from a teachers college in Guerrero state has again brought into the spotlight the pernicious influence of powerful drug gangs. The grisly incident was reportedly ordered by municipal officials and local police but executed by armed men linked to the Beltrán-Leyva organized crime syndicate.

The Sept. 26 attack has provoked unrest and widespread calls for federal authorities to extricate all levels of government from the corrupt grip of the kingpins. But with Mexico’s legacy of high-profile criminal enterprises, that is easier said than done.

A half-dozen major groups have traditionally controlled most of Mexico, but crackdowns started by former President Felipe Calderón have helped break these syndicates into dozens of splinter groups. That, in turn, has greatly challenged President Enrique Peña Nieto’s efforts to reign in organized crime.

Despite escalated and somewhat successful efforts by the administration of Peña Nieto to arrest top narco bosses, violence between the organizations — and their remnants — has resulted in tens of thousands of deaths in a conflict over turf and trade routes.