“Unfortunately, the attacks on abortion pills will not stop here — the anti-abortion movement sees how critical abortion pills are in this post-Roe world, and they are hellbent on cutting off access,” Nancy Northup, the president of the Center for Reproductive Rights, said in a statement. “In the end, this ruling is not a ‘win’ for abortion — it just maintains the status quo, which is a dire public health crisis.”

Abortion rights supporters argued that the challenge should never have ended up before the high court, because it was based on what many described as “junk science.” Two of the studies that anti-abortion groups had submitted to the court arguing that pills caused medical harm were retracted by medical journals.

Abortion rights and leading medical groups argue that the pills are “safer than Tylenol.”

“Decades of clinical research have proven mifepristone to be safe and effective, and its strong track record of millions of patient uses confirms that data,” Dr. Stella Dantas, president of the American College of Obstetricians and Gynecologists, said in a statement. “As the unanimous decision from the court makes clear in no uncertain terms, the people who brought this case were driven solely by a desire to impose their views on others and make it harder for patients to access safe, effective abortion care when they need it.”

Democratic leaders urged voters to stay energized to protect abortion rights, an issue that has driven gains for the party since the Supreme Court overturned Roe v. Wade two years ago. In a call with reporters, Julie Chavez Rodriguez, President Biden’s campaign manager, noted that the challenge to the abortion pills happened because of that decision by the court, which removed federal protections for abortion, and that the court overturned Roe v. Wade only because former President Donald J. Trump appointed three conservative justices.

She and Mini Timmaraju, the president of Reproductive Freedom for All, noted that Project 2025, drafted by groups supporting Mr. Trump, included a plan for him to direct the Food and Drug Administration to remove its approval of abortion pills. Trump allies are also pushing the revival of the Comstock Act, a 19th century anti-vice law, to prohibit mailing the pills even in states that allow abortion.