"The Spanish Revolution, like the Russian, also had its labor camps (campos de trabajo), initiated at the end of 1936 by Juan Garc¡a Oliver, the CNT Minister of Justice in the central government of Largo Caballero... The work camps were considered an integral part of the "constructive work of the Spanish Revolution," ...The CNT recruited guards for the "concentration camps," as they were also called, from within its own ranks. "

http://libcom.org/files/WorkersAgainstWork-Seidman_0.pdf