On Friday, a federal district judge permanently struck down an Arkansas law banning abortion at 12 weeks. The decision reinforces that state laws banning abortion prior to fetal viability are per se unconstitutional.

SB 134 was enacted in March of 2013 after a drawn-out legislative battle during which anti-choice lawmakers overrode a veto by Gov. Mike Beebe (D) to pass the measure. The legislation bans abortions in Arkansas at 12 weeks of pregnancy, defining fetal viability as “a medical condition that begins with a detectible heartbeat,” with only narrow exceptions in cases of rape, incest, and medical emergencies.

In April of 2013, attorneys from the American Civil Liberties Union (ACLU), the ACLU of Arkansas, and the Center for Reproductive Rights (CRR) sued to block the law, calling it one of the “most dangerous assaults on women’s health” in decades. CRR and the ACLU filed the lawsuit, Edwards v. Beck, in the U.S. District Court for the Eastern District of Arkansas on behalf of two physicians who provide abortion services in Little Rock, arguing that the Arkansas law violates the U.S. Constitution by banning pre-viability abortions. The physicians are represented by Stephanie Toti from CRR, Talcott Camp from the ACLU, and Bettina Brownstein and Holly Dickson of the ACLU of Arkansas.

In May, U.S. District Judge Susan Webber Wright temporarily blocked the law, which was set to take effect that summer. Friday’s ruling makes that temporary injunction permanent. “This ban would have inserted politicians into the deeply personal medical decisions of Arkansas women,” said Rita Sklar, executive director of the ACLU of Arkansas, in a statement. “We’re thankful that the court took the right step in striking it down, since this dangerous ban should never have been passed in the first place.”

While Friday’s decision blocked the law’s unconstitutional ban on pre-viability abortions, Judge Webber Wright’s ruling upheld a portion of the law that requires all women seeking an abortion to first undergo an abdominal ultrasound and receive statistical information in writing about carrying pregnancies to term if a fetal heart tone is detected. That provision, the court ruled, could be “severed” from the rest of the abortion restrictions in the law, holding that the ultrasound and other compelled disclosure requirements are “relevant to a woman’s decision making process” and “rationally related to the State’s interest in protecting the unborn.”

“While we are pleased that the court ultimately preserved women’s fundamental right to abortion, Arkansas women are fully capable of weighing their reproductive choices carefully and responsibly in consultation with their doctors—without politicians dictating what medical procedures or information they need,” said Nancy Northup, president and CEO of the Center for Reproductive Rights, in a statement.

Even though the court struck the pre-viability ban, it left intact the law’s definition of “viability,” a distinction that could prove important in future battles over abortion restrictions that attempt to push the threshold of what constitutes fetal viability in order to justify increasingly restrictive abortion regulations. “The Court notes that the foregoing statement conveys that viability ‘begins’ with a heartbeat; it does not declare that viability is fully achieved with the adept of a heartbeat,” Judge Webber Wright wrote. “Such a declaration would undoubtedly contravene the Supreme Court’s determination that viability in a particular case is a matter for medical judgment, and it is attained when, in the judgment of the attending physician on the particular facts of the case at hand, that there is a reasonable likelihood of sustained survival outside the womb.”

The Arkansas law is considered one of the most extreme anti-choice laws in the nation, even as more and more states consider pre-viability abortion bans. Last year, North Dakota passed a law that would have banned abortions as early as six weeks; that law is currently enjoined. And earlier this year, the U.S. Supreme Court refused to review a decision permanently blocking Arizona’s 20-week abortion ban, and courts in Idaho and Georgia have also recently blocked similar pre-viability bans.