Among the raft of abortion restrictions passed by states in the past few years, one did not initially gain much notice – a requirement that doctors performing abortions obtain admitting privileges at a local hospital.

But the measure, which 11 states have passed in some form, has proved an especially high hurdle for abortion providers to clear and a potent tool for antiabortion activists seeking to shut down abortion clinics.

Already, more than a dozen clinics have been shuttered in Texas as a result of that state’s admitting-privileges law, and at least one closed in Tennessee. Groups say clinics in Oklahoma, Louisiana and Wisconsin face the same fate if new laws there are permitted to take effect. Three of Alabama’s five clinics, and the last remaining clinic in Mississippi, would have shuttered if not for court decisions this month that stopped an admitting-privileges law from going into effect.

The state laws, on the surface, seem like a paperwork matter. They require physicians who perform abortions to forge relationships with hospitals so that they may treat patients there – a common-sense measure to protect women’s health in case of a botched abortion, foes of the procedure say.

In practice, many clinics have found getting these privileges very difficult. Their doctors often live too far away from the hospitals or cannot commit to admitting the minimum number of patients required for such a relationship. In other cases, hospitals have religious objections or have been reluctant to become embroiled in such a politically charged issue.

A doctor at the sole clinic in Mississippi, for instance, said his staff reached out to 13 hospitals to try to comply with the law. Six did not respond to their inquiries, and the rest informed them he would not qualify, he said.

Courts have differed in their opinions of such laws, and the matter may be taken up by the Supreme Court. If they are ultimately upheld, the impact could be “huge” compared with other abortion restrictions that have been passed recently, said Elizabeth Nash, state-issues manager for the Guttmacher Institute, a research organization that supports abortion rights.

“It has just really taken over, in a sense, because it has such the potential for shutting down clinics,” she said.

Antiabortion groups contend that if clinics are shutting down, that is only because they cannot meet basic safety standards. Requiring admitting privileges ensures that abortion doctors are vetted by their peers and prevents abortion doctors from simply abandoning their patients in trouble at the emergency room.

“The need for admitting privileges requirements is clear,” Denise Burke, vice president of legal affairs at Americans United for Life, said in an email.

Abortion rights proponents, however, argue that admitting privileges are medically unnecessary because anyone can be admitted to an emergency room. They regard the bills as a back-door attempt to shut down clinics in the wake of the antiabortion movement’s inability to overturn Roe v. Wade, the 1973 decision legalizing abortion nationwide.