PORTLAND — The future of a 39-foot buffer zone outside Planned Parenthood of New England offices was jeopardized Thursday by a U.S. Supreme Court decision striking down similar buffer zones.

By a 9-0 vote, justices ruled a Massachusetts law requiring anti-abortion activists to stay 35 feet away from offices where abortions are performed, excluding hospitals, violated the First Amendment.

In their ruling in McCullen v. Coakley, the justices said the requirement, a 2007 amendment to a law passed in 2000, violated activists’ rights to counsel patients outside a health-care center.

Portland City Councilors created a 39-foot buffer zone last November at 443 Congress St. as an emergency act. It was subsequently challenged in U.S. District Court in Portland in February. On June 18, Judge Nancy Torresen declined to strike down the city ordinance, citing the pending Supreme Court decision in the Massachusetts case.

City spokeswoman Jessica Grondin on Thursday said the city ordinance remains in effect for now, but will be studied.

“We need to conduct a review of the Supreme Court’s ruling to examine how it will apply to our buffer zone ordinance here in Portland,” Grondin said. “In regards to our pending legal case, we will wait to hear from the Court to see what the next steps are.”

Planned Parenthood of Northern New England spokeswoman Nicole Clegg, meanwhile, expressed dismay at the decision.

“The U.S. Supreme Court Justices’ decision today to strike down the buffer zone law shows a disregard for the safety of patients and staff entering reproductive health centers and we are disappointed by their decision to strike down the Massachusetts law,” Clegg said in a press release.

The city buffer zone effectively pushes activists across Congress Street and away from the entrance to Planned Parenthood.

The plaintiffs in the Portland case are Daniel and Marguerite Fitzgerald of Shapleigh, two of their children, and Richmond resident Leslie Sneddon.

Sneddon, Maine director for the California-based anti-abortion group Center for Bio-Ethical Reform, said in court documents she “counsels on the public sidewalk as part of her Christian ministry and out of a calling to treat her neighbors as thyself and always with compassion.”

In his majority opinion Thursday, Chief Justice John Roberts noted Massachusetts plaintiff Ellen McCullen does “’sidewalk counseling,’ which involves offering information about alternatives to abortion and help pursuing those options.”

Justice Antonin Scalia wrote a concurring opinion joined by Justices Anthony Kennedy and Clarence Thomas, and Justice Samuel Alito added his own concurring opinion.

Roberts noted buffer zones at facilities throughout Massachusetts prohibit the direct contact plaintiffs need for “sidewalk counseling,” while the original restrictions in the 2000 law led to “’no more than five or so arrests’ at the Planned Parenthood clinic in Boston.”

“It is no accident that public streets and sidewalks have developed as venues for the exchange of ideas,” Roberts said. “Even today, they remain one of the few places where a speaker can be confident that he is not simply preaching to the choir.”

Roberts suggested there are ways to remedy the harassment buffer zone supporters said patients have endured.

“While (Massachusetts) contends that individuals can inadvertently obstruct access to clinics simply by gathering in large numbers, that problem could be addressed through a law requiring crowds blocking a clinic entrance to disperse for a limited period when ordered to do so by the police,” the chief justice said.

David Harry can be reached at 781-3661 ext. 110 or dharry@theforecaster.net. Follow him on Twitter: @DavidHarry8.