The Polizia di Stato (State Police or P.S.) is one of the national police forces of Italy. It is the main police force for providing police duties and it is also responsible for highway patrol (autostrade), railways (ferrovie), airports (aeroporti), customs (together with the Guardia di Finanza) as well as certain waterways, and assisting the local police forces. It was a military force until 1981 when, with the Italian State Law 121, became a civil force, in contrast to the other main police forces of Italy, the Arma dei Carabinieri, which is a military police (gendarmerie) force and the Guardia di Finanza, the Italian customs and border protection police that also falls in the military corps category. The Polizia di Stato is the principal Italian municipal police force for the maintenance of public security as since it is run directly from the Dipartimento della Pubblica Sicurezza (Department of Public Security), and the keeping of public order (ordine pubblico).