When Hisui Tatsuta was in middle school, her mother used to joke that she couldn’t wait to see the faces of her future grandchildren. Ms. Tatsuta, now a 24-year-old model in Tokyo, recoiled at the assumption that she would someday give birth.

As her body began to develop feminine traits, Ms. Tatsuta took to extreme diet and exercise to forestall the changes. She started to regard herself as genderless. “To be seen as a uterus that can give birth before being seen as a person, I did not like this,” she said. Ultimately, she wants to be sterilized to eliminate any chance of becoming pregnant.

Yet in Japan, women who seek sterilization procedures like tubal ligation or hysterectomies must meet conditions that are among the most onerous in the world. They must already have children and prove that pregnancy would endanger their health, and they are required to obtain the consent of their spouses. That makes such surgeries difficult to obtain for many women, and all but impossible for single, childless women like Ms. Tatsuta.

Now, she and four other women are suing the Japanese government, arguing that a decades-old law known as the Maternal Protection Act violates their constitutional right to equality and self-determination and should be overturned.

During a hearing at Tokyo District Court last week, Michiko Kameishi, a lawyer for the plaintiffs, described the law as “excessive paternalism” and said it “assumed that we think of a woman’s body as a body that is destined to become a mother.”

Ms. Kameishi told a three-judge panel of two men and one woman that the conditions for voluntary sterilization were relics of a different era and that the plaintiffs wanted to take “an essential step in living the life they have chosen.”