In what could become a landmark case, the Supreme Court has begun debating whether transgender people should be required to undergo gender affirmation surgery in order to legally change their gender.

On Wednesday, the court’s Grand Bench heard the case of a transgender woman challenging a law that says only individuals who undergo sterilization surgery and lose their reproductive functions can have their gender changed in their family registry.

If the court deems as unconstitutional the surgery requirement for a gender change — which has been condemned both at home and abroad as inhuman and unnecessary — it is expected to pave the way for an amendment of the law to put it on par with global standards.

Legal experts say that when the Grand Bench considers a case, it means that the court may reverse an earlier judgment.

The 2003 law regarding people with gender dysphoria sets out five requirements for them to have their legal gender status changed through family court proceedings — in addition to a diagnosis of gender dysphoria by at least two medical doctors. Some requirements include the person needing to be age 18 or older, unmarried and have no underage children.

What’s particularly at issue are the remaining two conditions mandated by the law, which says the individual should “have no reproductive glands” or their reproductive glands should have “permanently” lost their function, and that they should have “a body that resembles the genital organs of those of the opposite gender.”

The plaintiff of the case — a transgender woman whose age is disclosed only as “under 50” to protect her privacy — lives “socially as a woman” but remains male in her family registry due to not having undergone gender affirmation surgery.

Her lawyers — Kazuyuki Minami and Masafumi Yoshida — argued on Wednesday that the last two requirements of the law violate her constitutional right to pursue happiness and live without being discriminated against.

In a statement issued by her lawyers at a news conference the same day, the plaintiff expressed her appreciation to the judges for having been able to express her true situation and feelings.

“I sincerely hope that, based on today's session and the statements made at yesterday’s hearing with the judges, a fair judgment will be reached in the end,” the plaintiff said.

While the plaintiff was not present at Wednesday’s session, she had met with the Supreme Court judges on Tuesday for a closed hearing, the lawyers said.

Two lower courts — Okayama Family Court in 2019 and a high court in western Japan in 2020 — denied the plaintiff’s request for a legal gender change. The Supreme Court is expected to hand down a decision by the end of this year.

In the lower court decisions, the judges ruled that the plaintiff failed to fulfill the requirement that the individual has to be "in a state of permanent lack of reproductive gland function."

The plaintiff, however, has asserted that she meets the requirements, having gone through years of hormone therapy — following a diagnosis of gender dysphoria — which has resulted in an “extreme decline” in her reproductive abilities. Therefore, she is essentially unable to reproduce without going through sterilization surgery, she argued.

“The situation undermines the right to have one's gender identity respected, which is a fundamental human right,” Minami argued in court.

Articles 13 and 14 of the Constitution guarantee that “all people shall be respected as individuals” and “are equal under the law and there shall be no discrimination.”

The lawyers also claimed that the plaintiff faces “significant disadvantages, difficulties and emotional distress” due to the “disparity between her socially lived gender and her legally recognized gender.”

In 2019, in a separate case involving a different person with similar claims, the Supreme Court consisting of four judges judged that the sterilization requirement does not violate the Constitution.

However, Wednesday’s case may have a different outcome since it was handled by the court’s Grand Bench, where 15 judges appeared, after a review of the case by the Petty Bench.

In the 2019 case, the judges said the requirement will not be regarded as violating the Constitution “at this time.” But as part of their supplementary opinion, two of the judges wrote that "the suspicion of a violation of the Constitution cannot be denied.”

In recent years, many countries have moved to eliminate similar sterilization clauses on the grounds that they violated human rights. In 2014, a group of international bodies including the World Health Organization, U.N. Human Rights Office and U.N. Women, released a statement saying coercive and involuntary sterilization of certain population groups — including transgender and intersex persons — should be eliminated.

According to fair, a group that supports sexual minorities, over 40 countries have either completely or partially eliminated such requirements.

In Japan, the issue remains divisive, and opposition to eliminating the surgery requirement runs strong in some conservative circles. On Sept. 8, a group of lawmakers from the ruling Liberal Democratic Party led by Upper House member Eriko Yamatani submitted a statement calling on the government to maintain all the requirements.

“If the surgery requirement were to be found unconstitutional, it would cause great confusion,” Yamatani posted on X, formerly known as Twitter.