The Tokyo District Court ruled on Thursday that Japan's dual nationality ban was constitutional, rejecting a claim by a teenage plaintiff who had lost his Japanese citizenship after acquiring British citizenship.

The 14-year-old plaintiff sued the state in 2023, saying his parents' decision to acquire British citizenship for him was invalid, citing Article 11 of the nationality law, which states individuals will lose their Japanese nationality when they acquire a foreign nationality “at their own choice.”

He also argued that the nationality law, itself, violates the Constitution if applied to a minor such as himself. In Japan, dual-nationals are asked to choose one nationality or the other before they reach the age of 22.