The Guarda Nacional Republicana, whose origins date back to 1801, at which time the Guarda Real de Policia (Royal Police Guard) was created, is a Security Force constituted by military elements that are organized in a Special Body of Troops, which actively and permanently veil for the execution of the law and are dedicated to the security and public order maintenance cause as well as to the protection and defence of the people and their goods. 

The Constitution of the Portuguese Republic, the National Defence and Armed Forces Law, the Internal Security Law and the Law on the General Basis of the Military Condition constitute the institutional juridical framework on which the legislation of the present Guarda Nacional Republicana (GNR) is based.