The decision, one day before the provision was to take effect, prevented a major disruption of the abortion clinics in Texas. It was a victory for abortion rights groups and clinics that said the measure served no medical purpose and could force as many as one-third of the state's 36 abortion clinics to close.
But the court upheld a second measure, requiring doctors to use a particular drug protocol in nonsurgical, medication-induced abortions that doctors called outdated and too restrictive.
In a decision that is widely expected to be appealed to higher courts, Judge Lee Yeakel of United States District Court in Austin declared that "the act's admitting-privileges provision is without a rational basis and places a substantial obstacle in the path of a woman seeking an abortion of a nonviable fetus."
The ruling was hailed by the chief executive of Whole Woman's Health, a private group that had warned that it could be forced to close its clinics in McAllen, Fort Worth and San Antonio because they use visiting doctors who could not obtain admitting privileges locally. "We are very relieved," said the official, Amy Hagstrom Miller.
In bringing the suit against two parts of a sweeping anti-abortion law adopted in July, abortion rights groups said that these provisions would have "dramatic and draconian" effects on women's access to the procedure. But lawyers for the state argued that the predictions were exaggerated and that the measures served the state's interest in "protecting fetal life."
Gov. Rick Perry, who has said he hopes to make abortion "a thing of the past," signed the legislation in July. It had been temporarily derailed when Wendy Davis, a Democratic state senator, mounted an 11-hour filibuster in the Republican-controlled Legislature. Ms. Davis is now running for governor of Texas, with abortion rights one of her planks.
Mr. Perry responded swiftly to Monday's decision, vowing in a written statement to appeal: "We will continue fighting to implement the laws passed by the duly elected officials of our state, laws that reflect the will and values of Texans."
The lawsuit did not challenge two other central provisions of the Texas law: a requirement that all abortion clinics meet the costly standards of ambulatory surgery centers, which does not take effect until September 2014, and a ban on nearly all abortions at 20 weeks after conception, which will take effect on Tuesday.
Anti-abortion groups, while disappointed with the finding on admitting privileges, said they looked forward to an appeal and they described the imminent 20-week ban as a victory.
In three days of hearings before Judge Yeakel last week, lawyers for the state argued that it was impossible to know in advance how many clinics would be shut by the admitting-privilege rule and that, in any case, the rule would not pose an "undue burden" on women seeking abortions, which would remain available in the state.
Solicitor General Jonathan Mitchell also asserted that the law served the state's interest in "protecting fetal life."
The plaintiffs said the disputed provisions did not serve any medical interest and were intended to prevent women from exercising their constitutional right to an abortion.
The legal challenge was brought by the American Civil Liberties Union, the Center for Reproductive Rights, Planned Parenthood of Greater Texas and several other Texas clinic owners.
In the hearings, clinic owners described why the visiting doctors used by many clinics could not meet the admitting-privilege requirement and the hardships patients would face, especially in sparsely populated West Texas, if clinics closed. Similar admitting-privilege requirements have been blocked by courts in Alabama, Mississippi, North Dakota and Wisconsin.
Doctors described the professional consensus that medication abortions were safe and effective through nine weeks of pregnancy, and with a lower dosage than that used in the earliest trials. They said that the Texas law's mandate to use the protocol approved by the Food and Drug Administration in 2000, which approved use of higher doses through only seven weeks of pregnancy, would expose women to unnecessary risk.
Courts in North Dakota and Oklahoma have struck down laws imposing the earlier drug protocol for medication abortions, but one remains in effect in Ohio.
Judge Yeakel ruled Monday that requiring the earlier protocol did not pose an unconstitutional obstacle except in cases where the new regime appeared necessary to save the life or health of the mother. It remains to be seen how that will be interpreted, but the Texas plaintiffs expressed concern.
"While this ruling protects access to safe and legal abortion for women in many parts of the state, it puts ideology over science by banning a safe method of abortion for many women," said Cecile Richards, president of the Planned Parenthood Federation of America, referring to the rules on medication abortion.
Texas was the 12th state to adopt a 20-week ban, which legal experts say is in conflict with Supreme Court decisions granting a right to abortion until the fetus is viable outside the womb, usually at around 24 weeks. Courts have blocked such measures in the three states where they have been challenged, but they remain in effect in others.
Rights groups said they were still studying when and how to challenge the ban.
Of the current case, Judge Yeakel said that "at the end of the day these issues are going to be decided definitively not by this Court, but by either the Circuit or the Supreme Court of the United States." To speed the appeals, he took the unusual step of issuing his final decision, rather than a preliminary injunction.
This article has been revised to reflect the following correction:
Correction: October 28, 2013
An earlier version of this article misspelled the name of a group that operates abortion clinics in Texas. It is Whole Woman's Health, not Whole Women's Health.
