(Reuters/Chris Kenning)A protester (L) and an escort who ensures women can reach the clinic stand outside the EMW Women's Surgical Center in Louisville, Kentucky, U.S. January 27, 2017.

A federal judge has upheld a city ordinance that is aimed at keeping protesters away from the entrances of abortion clinics in Pittsburgh, Pennsylvania.

In a ruling issued on Thursday, U.S. District Judge Cathy Bissoon said that the 15-foot "buffer zone" outside abortion clinics in the city "imposes only a minimal burden" on protesters trying to persuade women not to terminate their pregnancies.

The judge also noted that the clinic protesters' own records had shown that they are still able to communicate with patients despite the buffer zone, and in some instances, they have accomplished their goal of persuading women not to have abortions.

Pro-life activists challenged the ordinance in court in September 2014, shortly after the U.S. Supreme Court overturned an expansive statewide buffer zone law in Massachusetts.

Bissoon had initially dismissed the case, but it was reinstated by the Third U.S. Circuit Court of Appeals in June 2016. The appellate court had ruled that before a decision can be made about the case, the city must first show that the buffer zones served a legitimate public interest and that it had reasons not to use other approaches that might be less restrictive.

In her decision on Thursday, Bissoon pointed to a 2005 City Council testimony which noted that nine months before the passage of the ordinance, there had been "13 cases of aggressive pushing, shoving and hitting, and 30 complaints of harassing behavior" outside clinics.

The judge noted that the city had tried other approaches, such as stationing police officers at the clinics, which later proved to be impractical.

Protesters have argued that they would be able to persuade women not to abort if there were no buffer zones, but Bissoon said that they "offer no concrete evidence to support this claim."

Bissoon's decision has been hailed by city officials and other pro-choice activists. "We thank the court for this decision, which retains a great benefit for women and health care access in Pittsburgh," said Timothy McNulty, spokesman for Mayor Bill Peduto, according to Pittsburgh Post Gazette.

The Alliance Defending Freedom (ADF), which represented the clinic protesters, said that it is currently consulting its clients regarding the possibility of appeal.

"The government can't stifle free speech simply because some pro-abortion politicians or activists demand it," said ADF Senior Counsel Kevin Theriot.

"The district court should have ruled in accordance with the appeals court, which correctly applied what the Supreme Court made clear three years ago — that free speech receives the highest protection on public sidewalks," he added.