In this September 2019 file photo, tennis player Naomi Osaka, who was born with Japanese and American citizenship, is seen during a match in Osaka's Nishi Ward. (Mainichi/Tadashi Kako)

TOKYO -- Japan's Nationality Act, which forbids multiple citizenship, is again in the spotlight after tennis player Naomi Osaka selected Japanese citizenship over American nationality in 2019. Meanwhile, there is an ongoing legal battle being waged by plaintiffs arguing that the law is unconstitutional.

Over 70% of member states of the United Nations permit their people to have more than one citizenship. In a world where it's become quite common to see individuals from diverse backgrounds and for people to compete on the global stage, some experts are demanding that Japan do the same.

The Japanese Nationality Act stipulates that a child born to a Japanese parent is legally Japanese. Meanwhile, some nations have a system where a child born in such countries to a Japanese parent becomes a dual citizen of that place and Japan.

The Japanese law requires anyone who was born with or obtained multiple nationality before the age of 20 to pick one of them before their 22nd birthday. Those who acquire citizenship of another country after turning 20 must decide which one to keep within a two-year period.

Naomi Osaka held both Japanese and U.S. citizenships but decided to keep her Japanese citizenship before she turned 22. Her choice has been seen as an indication of her desire to compete in the upcoming Tokyo Olympics as a Japanese tennis player.

But because individuals who choose to keep their Japanese nationality are only "obliged to make an effort" to give up other citizenships, there are people in Japan who continue to hold two or more passports. According to a 2018 estimate by the Justice Ministry, about 925,000 Japanese have multiple citizenship.

Furthermore, foreigners wanting to acquire Japanese nationality are required to submit a certificate showing they have forfeited their original citizenship. But those from countries without renunciation procedures can also become dual citizens. On the other hand, Japanese people who choose a foreign nationality "of their own will" automatically have their Japanese citizenship revoked.

Hitoshi Nogawa, 76, a businessperson from Switzerland, is one of eight plaintiffs who have filed a suit against the Japanese government arguing that "depriving people who obtained foreign nationality of Japanese citizenship against their will is a violation of the Constitution, which guarantees the right to pursue happiness and other privileges."

Nogawa, who effectively lost his Japanese citizenship for acquiring Swiss nationality, said, "I identify as Japanese, but it feels like I've become half a person. I feel bad for my ancestors and, in the current situation, I don't plan on being buried with them."

Born in Kanagawa Prefecture, south of Tokyo, Nogawa moved to Switzerland in his 20s and established a trading company. In order to bid on a public works project, he needed Swiss citizenship, which he obtained in 2001. He did not encounter any trouble until 2013, when he was told by the Japanese Embassy there, "If you don't choose one (nationality), it's going to be a problem."

The request is based on the Nationality Act, which stipulates that people who acquire foreign citizenship lose their Japanese nationality, and requires them to submit a citizenship renunciation notification.

For Nogawa, giving up his Swiss nationality would have posed a problem for his work and discarding his Japanese citizenship would have meant losing his identity. Caught in a dilemma, he refused to respond to the embassy's request and did not submit the notification. In 2015, he tried to renew his Japanese passport but was rejected. To this day, he has not been able to renew it.

Nogawa and seven others living overseas filed a suit with the Tokyo District Court in March 2018. Six of the plaintiffs, who have already acquired citizenships of different countries, are demanding confirmation that they are in possession of their Japanese citizenship, and two others who seek to obtain foreign nationality are looking for confirmation that they will not lose their Japanese citizenship when they do so.

The stipulation in the Nationality Act that bans multiple citizenship has not been revised since it first went into force under the Meiji Constitution, Japan's prewar and wartime supreme law. Teruo Naka, a lawyer of the plaintiffs' legal team says the law "does not correspond to the flow of the times."

In contrast, the government argues that "people having multiple citizenship could cause friction between nations depending on which country's protection they come under" among other counterarguments. The Justice Ministry, which enforces the Nationality Act's provisions, explains that "the withdrawal of Japanese citizenship is not a deprivation, and reacquisition is allowed if necessary." The suit is proceeding at the district court.

As of 2019, around 150, or 75% of United Nations member states, permit multiple nationalities. The Universal Declaration of Human Rights provides that "no one shall be arbitrarily deprived of his nationality nor denied the right to change his nationality."

Teru Sasaki, professor of transnational sociology at Aomori Public University, conducted an online survey of Japanese citizens in 2019, in which around 60% of the 3,171 respondents supported the option, "Japanese citizens who obtain a foreign nationality should not have to lose their Japanese citizenship."

The study results suggest that "society is tolerant of multiple nationalities, and there is a gap between the sense of ordinary citizens and the legal system," said Sasaki.

Employment regulations for some civil servants, including Diet members, require that they have Japanese citizenship, and people who have foreign nationality cannot become diplomats. To permit multiple citizenship, discussions on job restrictions may also be necessary.

(Japanese original by Asako Takeuchi, City News Department)