A New York county clerk on Thursday blocked Texas from filing a legal action against a New York doctor for prescribing and sending abortion pills to a Texas woman.

The unprecedented move catapults the interstate abortion wars to a new level, setting the stage for a high-stakes legal battle between states that ban abortion and states that support abortion rights.

The dispute is widely expected to reach the Supreme Court, pitting Texas, which has a near-total abortion ban, against New York, which has a shield law that is intended to protect abortion providers who send medications to patients in other states.

New York is one of eight states that have enacted “telemedicine abortion shield laws” after the Supreme Court overturned the national right to an abortion in 2022. The laws prevent officials from extraditing abortion providers to other states or from responding to subpoenas and other legal actions — a stark departure from typical interstate practices of cooperating in such cases.

The action by the New York county clerk is the first time that an abortion shield law has been used.

This case involves Dr. Margaret Daley Carpenter of New Paltz, N.Y., who works with telemedicine abortion organizations to provide abortion pills to patients across the country. In December, the Texas attorney general, Ken Paxton, sued Dr. Carpenter, who is not licensed in Texas, accusing her of sending abortion pills to a Texas woman, in violation of the state’s ban.

Dr. Carpenter and her lawyers did not respond to the lawsuit and did not show up for a court hearing last month in Texas. Judge Bryan Gantt of Collin County District Court issued a default judgment, ordering Dr. Carpenter to pay a penalty of $113,000 and to stop sending abortion medication to Texas.

On Thursday, citing New York’s shield law, the acting clerk of Ulster County in Kingston, N.Y., Taylor Bruck, said he would not grant Texas’ motion seeking to enforce the Collin County order. He also refused to allow Texas to file a summons that sought to force Dr. Carpenter to pay the penalty and comply with the Texas ruling.

“In accordance with the New York State Shield Law, I have refused this filing and will refuse any similar filings that may come to our office,” Mr. Bruck said in a statement. “Since this decision is likely to result in further litigation, I must refrain from discussing specific details about the situation.”

New York’s attorney general, Letitia James, had previously sent guidance to courts and officials throughout the state, directing them to follow the shield law and indicating how they could comply and which specific actions were prohibited.

“I commend the Ulster County Clerk for doing what is right,” Ms. James said in a statement. “New York’s shield law was created to protect patients and providers from out-of-state anti-choice attacks, and we will not allow anyone to undermine health care providers’ ability to deliver necessary care to their patients. My office will always defend New York’s medical professionals and the people they serve.”

The Texas attorney general’s office did not immediately respond to a request for comment. Legal experts said that a likely next step would be for Texas to file a challenge to the shield law in a state or federal court in New York.

Texas was the first state with an abortion ban to initiate legal action against abortion providers in states with shield laws. In January, the first criminal charges against a shield-law abortion provider were filed in a second state, Louisiana. In that case, a state grand jury issued a criminal indictment, also against Dr. Carpenter, accusing her of violating Louisiana’s near-total abortion ban by sending pills to that state.

Last month, Louisiana officials issued an extradition order for Dr. Carpenter, which was immediately rebuffed by New York’s governor, Kathy Hochul.

“I will not be signing an extradition order that came from the governor of Louisiana — not now, not ever,” Ms. Hochul said then.

Dr. Carpenter and her lawyers have not commented about either the Texas or Louisiana case. The Abortion Coalition for Telemedicine, an organization Dr. Carpenter co-founded, has issued statements in response to the cases. “Shield laws are essential in safeguarding and enabling abortion care regardless of a patient’s ZIP code or ability to pay,” the coalition has said. “They are fundamental to ensuring everyone can access reproductive health care as a human right.”

Telemedicine abortion shield laws have become a key strategy for supporters of abortion rights. Under these laws, which have been in use since summer 2023, health care providers in states where abortion is legal have been sending more than 10,000 abortion pills per month to patients in states with abortion bans or restrictions.

The Texas lawsuit accuses Dr. Carpenter of providing a 20-year-old woman with the two medications used in a standard abortion regimen, mifepristone and misoprostol. Typically used up through 12 weeks into pregnancy, mifepristone blocks a hormone needed for pregnancies to develop, and misoprostol, taken 24 to 48 hours later, causes contractions similar to a miscarriage.

According to a complaint filed by the Texas attorney general’s office, the woman, who had been nine weeks pregnant, asked the “biological father of her unborn child” to take her to the emergency room in July “because of hemorrhage or severe bleeding.” The man “suspected that the biological mother had in fact done something to contribute to the miscarriage,” the suit said, and he went back to their home in Collin County, where he “discovered the two above-referenced medications from Carpenter.”

In the Collin County court hearing last month, Ernest C. Garcia, chief of the administrative law division in the attorney general’s office, said that the man “then filed a complaint with the Texas Attorney General’s Office.”