Defection

[2][3] This term is also applied, often pejoratively, to anyone who switches loyalty to another religion, sports team, political party, or other rival faction.

[4][5] The physical act of defection is usually in a manner which violates the laws of the nation or political entity from which the person is seeking to depart.

For example, in the 1950s, East Germans were increasingly prohibited from traveling to the western Federal Republic of Germany where they were automatically regarded as citizens according to Exclusive mandate.

During the Cold War, the many people illegally emigrating from the Soviet Union or Eastern Bloc to the West were called defectors.

Some of the more famous cases were British spy Kim Philby, who defected to the USSR to avoid exposure as a KGB mole, and 22 Allied POWs (one Briton and twenty-one Americans) who declined repatriation after the Korean War, electing to remain in China.