Latvian nationality law

The Latvian nationality law is based on the Citizenship Law of 1994 (as at 2013, amended four times, most recently through the amendments approved by the Parliament of Latvia on May 9, 2013). It is primarily based on jus sanguinis.

Dual citizenship is not prohibited by Latvian citizenship law. According to the amendments to the Citizenship Law which came into force on 1 October 2013, citizenship of Latvia may be retained for persons who have acquired:
Citizenship of another EU Member State or another EFTA Member State;
Citizenship of another NATO Member State
Citizenship of Australia, Brazil or New Zealand;
Citizenship of such a country with which Latvia has concluded an agreement on the recognition of dual citizenship (no such agreement is currently concluded);
Citizenship of a country not referred to previously if due to important national interests permission from the Government of Latvia is received to retain dual citizenship;
Citizenship of a country not referred to previously if it has been acquired automatically (ex lege), through marriage or as a result of adoption.
Children of citizens of Latvia may hold dual citizenship with any country. Some countries, such as Japan, however, do not permit their nationals to also, after reaching adulthood, hold a foreign citizenship. A dual Latvian-Japanese national must declare, to the East Asian country's Ministry of Justice, his or her intention as to which citizenship to keep, before turning 22.

Before October 1, 2013, the newly acquired non-Latvian citizenship is simply not recognised by the Republic of Latvia, with the exception of a transitional clause: Latvia allows dual citizenship for those and their descendants who were forced to leave Latvia during the Soviet or Nazi occupations and adopted another citizenship while away from Latvia. In order to be eligible for dual citizenship, they had to claim it by July 1, 1995. If such a claim is made after this date, they shall renounce the citizenship of another state. If by a law of another state a Latvian citizen may be a citizen of this state, in relations with Latvia this person is considered solely as a Latvian citizen.

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Wikipedia