The police collect or maintain a major share of local records for the _obshtina_ people's councils. These records deal with vital statistics, citizenship, identification, travel visas, registration of residences, licenses and permits, and employment data. A person acquires Bulgarian citizenship in the circumstances that are accepted in most other countries--by ancestry, place of birth, or naturalization--but there may be somewhat more than the usual number of situations in which he may lose it. Persons are deprived of citizenship if they leave the country unlawfully, leave lawfully but fail to return within a reasonable time after their visas expire, go abroad to avoid military service, acquire foreign citizenship in a manner not specified in Bulgarian law, or if they conduct themselves abroad in ways that are contrary to Bulgaria's interests or that are unworthy of a Bulgarian citizen. Persons not ethnically Bulgarian are released from their citizenship upon emigration, although they are not released unless all of their obligations in the country are settled. Laws governing the stay of foreigners in the country also are administered and enforced by the militia. According to the revised law that took effect in 1972, the whereabouts of a foreigner is subject to the same rules that apply to Bulgarian citizens. His hotel or other local address, therefore, must be reported to the militia within twenty-four hours of his arrival at each stop. Tourists are usually unaware that such detailed records of their stays are being maintained, because hotel personnel ordinarily take care of the reporting. If the visitor stays at the home of a Bulgarian, that citizen must report his presence on the same twenty-four-hour basis. A foreign visitor may travel freely otherwise, except that he may not go to certain restricted areas or to the border zone at any place other than at one of the designated crossing points. He must leave the country when the time specified in his visa has expired unless he has a criminal charge against him and is awaiting trial, has been sentenced and is serving a term in prison or at a correctional labor camp, or has the obligation to provide support for a person in the country. Border Troops The Border Troops are part of the Bulgarian People's Army and are organized within the Ministry of National Defense. Border units resemble regular military forces more than they do the police. They are considered militarized security units, and some 15,000 men serve in them.