In 212, the "Constitutio Antoniniana", issued by the emperor Caracalla, granted Roman citizenship to all the inhabitants of the empire, thus ending the second-class "peregrini" status. This made military diplomas largely redundant, and indeed the last known auxiliary diplomas date from AD 203. But diplomas for service in the navy, Praetorian Guard cavalry and the "cohortes urbanae" continued to be issued until the late 3rd century. This might be explained by the fact that "barbari" (foreigners from outside the Roman empire) were still recruited for those units.