“I say it, gentlemen: I am a lawyer who broke the law,” she declared in court. She received a disciplinary summons but maintained in subsequent appearances that she had done the right thing, asserting, “Sometimes it is necessary to break the law to move forward and bring about a change in society.”

Ms. Chevalier was acquitted because she was considered to have suffered from “moral, social and family constraints that she could not resist,” the website of France’s justice ministry said.

When the verdict was rendered, she was fined 500 francs and released, while activists chanted her name in the streets. Four others, including her mother, had been charged as accomplices and were absolved.

The case, with its young protagonist and its high-profile lawyer, became a cause célèbre and a catalyst in the feminist campaign to overturn the law. Among those who joined was Simone Veil, the French health minister and a survivor of Auschwitz, who endured an avalanche of personal attacks but kept pushing for change. And on Jan. 17, 1975, France enacted the Veil Law, decriminalizing abortion.

This was two years after the U.S. Supreme Court had legalized abortion in the United States in Roe v. Wade. As in France, it had taken a pregnant woman, a Dallas waitress named Norma McCorvey, under the pseudonym Jane Roe, to challenge the law and achieve a major victory for women.

Although Ms. Chevalier was proud of the effect her case had had, she loathed the publicity and shunned the notion of exploiting it for fame or profit. “It’s not my style to build on what has screwed me up,” she said in a rare interview in 2019, with the French newspaper Libération.

Still, her story has been packaged and repackaged for public consumption in a radio series, a television movie and theatrical productions, including a play in 2019 at the Comédie-Française called “Hors la Loi” (“Outlaw”). A blue metal footbridge in front of the Bobigny court was dedicated in her name.