it difficult to prove avoidance of residency registration and so to prosecute. De facto citizens have no restriction on where they reside (with the exception of closed cities or near borders). Still, many civil rights are dependent on registration, such as the right to vote. In November 2010, the Federal Migration Service announced the possible cancellation of internal passports, which, if it were implemented, would be replaced by plastic ID cards or drivers' licenses. In 2013, a plastic ID card, Universal electronic card was introduced, and any citizen had the right to reject it and retain an old-style internal passport. This card system was abandoned in January 2017. Belarus In Belarus, internal passports and passports for travelling abroad were merged into one kind of document in 1991. Passports are the primary means of identification for citizens of Belarus both in homeland and abroad. Belarusian citizens must have a passport after they have reached the age of 14; passports can also be issued to younger children for travelling abroad. Passports are valid for 10 years regardless of age. Apart from visa pages, a considerable number of pages in Belarusian passports are designated for "internal" records, such as place of residence and marriage. Citizens had to obtain special stamp enabling the passport bearer to cross the border of the Union State before 2005 when the Constitutional Court ruled the practice not conforming to the Constitution. Combination of primary identification document with international passport causes significant inconvenience to bearers who cannot certify their identity while their passports are processed for visas in embassies and consulates. A passport can also be easily invalidated by a careless foreign passport control official by placing a stamp in a reserved page. China and neighbors The internal passport system in China and some neighbors evolved from an ancient huji system of family register. The system has evolved to manage internal movement, distribution of welfare, and other rights. People's Republic of China The People's Republic of China (PRC) maintains a system of residency registration in mainland China known as hukou, by which government permission is needed to formally change one's place of residence. It is enforced with identity cards. This system effectively controlled internal migration before the 1980s, but subsequent market reforms caused it to collapse as a means of migration control. An estimated 150 to 200 million people are part of the "blind flow" and have unofficially migrated,