Clinics in Missouri were preparing to restore access to medication abortions for the first time in nearly a decade on Friday after a judge there struck down dozens of state laws that had effectively undermined a constitutional amendment guaranteeing reproductive rights.

The ruling by Judge Jerri Zhang of Jackson County Circuit Court, which includes Kansas City, largely sided with Planned Parenthood and the American Civil Liberties Union of Missouri. The groups had argued that abortion restrictions passed over time by the state legislature, which has been controlled by Republicans for more than two decades, were thwarting the will of the voters, who overturned a near-total ban on abortions in 2024.

“Debate and litigation around the topic of abortion has occurred for several decades,” the judge wrote. “It is a deeply personal, philosophical, and moral issue to many on both sides of the argument.”

But, she found, most of the approximately 40 state laws contested by the abortion rights groups were at odds with the 2024 ballot measure, which enacted a “fundamental right to reproductive freedom” in Missouri and barred the government from interfering with it.

Catherine Hanaway, the Missouri attorney general, called the judge’s decision “radical” and “a free pass” for self-policing by abortion providers, and vowed in a statement to “expeditiously” appeal it to the Missouri Supreme Court.

Emily Wales, the president and C.E.O. of Planned Parenthood Great Plains, hailed the decision, saying that it “brings compassion and common sense back to Missouri health care.”

Gillian Wilcox, director of litigation at the A.C.L.U. of Missouri, called it a “monumental win” and “a reminder that politicians are trying to strip us of our right to reproductive freedom.”

Ms. Wilcox pointed to a measure state lawmakers have placed on the November ballot asking voters to abandon the 2024 amendment.

The new amendment, if passed, would ban abortion except in medical emergencies, or in cases of rape or incest if the assault is reported to the police within 48 hours and the pregnancy is less than 12 weeks along. The measure also would prohibit gender transition procedures for minors.

The decision marked the latest turn in a legal battle that has roiled Missouri since 2022, when the Supreme Court struck down federal abortion protections in Dobbs v. Jackson Women’s Health Organization. After that ruling, which overturned Roe v. Wade, Missouri enacted one of the nation’s earliest and most comprehensive abortion bans.

Two years later, Missouri voters narrowly overturned the ban, approving a broad, citizen-sponsored reproductive rights amendment. Seeking to quickly align state law with the initiative, lawyers from the Planned Parenthood Federation of America, the A.C.L.U. of Missouri and other abortion rights groups sued in late 2024 on behalf of local Planned Parenthood affiliates.

Providers argued that regulations passed by conservative lawmakers over decades made it practically difficult to implement the amendment. Extensive licensing mandates, insurance rules, wait times, tissue-handling procedures, telemedicine restrictions and other requirements particular to abortion providers still constrained access, they said.

State officials contended that the state laws were needed to protect patients. But providers said that the laws made it difficult to obtain even relatively uncomplicated methods of early pregnancy termination, such as abortion pills, which are used in about two-thirds of abortions in the United States.

That method, also known as a medication abortion, generally involves a two-pill regimen of mifepristone, which blocks a hormone necessary for pregnancy to continue, followed 24 to 48 hours later by a second medication, misoprostol, which causes contractions similar to a miscarriage. It typically is prescribed during the first 12 weeks of pregnancy.

In 2021, during the coronavirus pandemic, the F.D.A. began allowing mifepristone to be prescribed by telemedicine and sent to patients by mail after data showed it was safe and effective to take the pills without seeing a health care provider in person. After the Dobbs decision, medication abortions became a flashpoint in states seeking to end the procedure. At least one high-profile abortion case already has reached the Supreme Court.

In 2024, Judge Zhang, who was appointed by a Republican governor in 2021, ruled that Missouri’s 2022 abortion ban was unconstitutional and issued a preliminary injunction against one of the contested state laws, a statute mandating wait periods. Two months later, in early 2025, she issued another preliminary injunction, this one against a licensing requirement for abortion clinics. The rulings set the stage for Planned Parenthood to resume abortion procedures in-person.

The Missouri Supreme Court again blocked access, finding that the judge had failed to meet the legal standard necessary to halt state statutes.

In January, Judge Zhang held a 10-day bench trial in Kansas City in which she heard from providers, insurance experts, government health officials and women who had undergone abortions as far back as 1976 and who “now regret their decisions, or who otherwise suffered traumatic abortion experiences.”

Her final ruling on Thursday largely sided with abortion rights groups, but let stand a handful of limits. Among them were requirements that abortions be performed by physicians rather than nurses or advanced practice clinicians, and that patients be examined in person at least initially.