The city rejected the registration submitted by her current husband on Nov. 10, citing a provision in the Civil Code — Paragraph 2 of Article 772 — that says a child born within 300 days from the date of the dissolution or cancellation of a marriage is deemed to have been conceived during the time the couple were married. The woman was separated from her former husband for a much longer period, according to the lawyer.

The suit, to be filed with the Okayama District Court, claims the city violated the Constitution. While the provision has recently been criticized for not addressing the reality of matrimonial relations, it is unusual that a lawsuit is filed on grounds that a refusal to register a baby based on the provision goes against the egalitarian principle of the Constitution.

The Justice Ministry issued a notice in May 2007 that municipal governments should grant registrations to babies born within the 300-day window — either born to the current spouse or out of wedlock — if pregnancy is proved to have taken place after a divorce.

The notice, however, does not cover cases where, like the woman in question, the divorcing couple had protracted negotiations and a woman gives birth with a new partner.

"It is unreasonable discrimination to treat children differently between those conceived before divorce and those after," the woman said. Her lawyer said, "We would like to eliminate inadequacies in the law."

According to the lawsuit, the woman, in her 20s, married her previous husband in February 2006 but separated that September after he physically abused her.

The woman filed for divorce in March 2007 with the Okayama court and the court granted it, but her former husband appealed. The couple's divorce was finalized in March this year.

The woman married her current husband in October and gave birth to a baby girl Nov. 4.

The current husband presented a registration for the baby on Nov. 10 to the city of Soja, but the city refused, noting the birth came within 300 days after her divorce and she is presumed to have gotten pregnant around February, before her divorce became official.

The baby thus remains unregistered.

The mother is planning to file the compensation suit on behalf of the baby.

To join the registry of the current husband, the couple have also filed with the Okayama Family Court to have the baby recognized as being born to the man.