A Taiwanese national and legally recognized permanent resident of Japan filed suit Monday with the Tokyo District Court against the Justice Ministry for rejecting his application for naturalization.

Hsiao-Ming Wu, a resident of Japan since 1979 and the son of a naturalized Japanese citizen, was informed verbally in March that he could not become a naturalized citizen because he had spent more than 180 days in 1997 outside of Japan. Wu's application was officially turned down in May.

That a foreigner must spend a certain amount of time in Japan during the year of his application for naturalization is an internal rule within the ministry that is not publicly disclosed, said Wu's lawyers. "This is clear evidence that there is black box in which the Justice Ministry sets its guidelines," said Yuji Nanameki, one of Wu's lawyers.

As president of a trading company, Wu says he is obliged to spend a significant portion of each year abroad on business, while his wife and 3-year-old son remain at the family's Tokyo home.

The ministry failed to provide the applicant an opportunity to explain the reasons for their absence from the country, the lawyers said. "Such a practice by the ministry is discriminatory and violates applicants' freedom to choose an occupation," Wu's lawyers said. "Policies like this prevent Japan from gaining the international mind set of foreigners who care for Japan and want to work and live here," Wu said. "They are sad and must be changed."