An escort for Planned Parenthood keeps her toes on a white line defining an edge of the buffer zone.

BOSTON (AP) - A federal appeals court Monday upheld a Massachusetts law requiring buffer zones to keep protesters away from abortion clinics.

The law, passed by the state legislature a year ago, forces protesters to stay at least 18 feet away from clinics where abortions are performed, and at least six feet away from women entering the clinics. Abortion opponents said the law violated their free speech rights.

Three anti-abortion protesters who opposed the law said it was unfair to allow clinic employees to escort women inside clinics while holding back demonstrators.

Massachusetts Attorney General Thomas Reilly called Monday's decision by the 1st U.S. Circuit Court of Appeals a "victory for women seeking health services."

"The buffer zone law is a sensible measure that strikes the right balance between public safety and the right to free speech," Reilly said.

Dwight Duncan said he and other lawyers for the plaintiffs would study the ruling before deciding whether to pursue an appeal to the U.S. Supreme Court. A similar Colorado law was challenged by anti-abortion protesters but upheld last year by the Supreme Court.

"I think we're disappointed because we were hoping for better - more vigilance as far as the First Amendment is concerned from the 1st Circuit," Duncan said.

Lawmakers began pushing for the law after gunman John Salvi killed two workers at abortion clinics in 1994.