WASHINGTON (CNN) -- The Supreme Court will step back into the national debate over free speech and abortion, accepting an appeal Monday on the rights of protesters outside medical clinics.

A challenge to a Massachusetts law concerns government-mandated buffer zones set up around facilities that perform abortions. Oral arguments and an eventual ruling are not expected until next year.

The state's "selective exclusion law" makes it a crime for speakers other than clinic "employees or agents ... acting within the scope of their employment" to "enter or remain on a public way or sidewalk" within 35 feet of "a reproductive health care facility."

Anti-abortion activists say the law has kept them from talking with patients approaching the clinic entrances. But a federal appeals court in January said "the right of the state to take reasonable steps to ensure the safe passage of persons wishing to enter health care facilities cannot seriously be questioned."

The court had rejected a similar challenge to the law four years ago. Municipalities in Montana, Colorado, Florida, California and elsewhere have enacted similar "fixed" and "floating" buffer zone laws.

The Massachusetts case is McCullen v. Coakley (12-1168).

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