Civil disobedience, including methods such as those used by the Rev. Martin Luther King Jr. and his followers, is threatened by the government's application of organized-crime laws to antiabortion protesters who staged aggressive blockades and sit-ins at women's health centers in the 1980s and '90s, attorneys for the protesters told the Supreme Court yesterday.

"Classic protest actions venerated in American history would be crimes," Roy Englert, who represents leaders of the Pro-Life Action League, told the court. Englert's clients, along with Operation Rescue, were found liable in 1998 by a Chicago jury for acts of coercion and violence that violated federal racketeering and extortion laws. The jury awarded more than $250,000 in damages to clinics in Milwaukee and Delaware, and a federal judge later ordered a permanent nationwide halt to the protests.

The U.S. Court of Appeals for the 7th Circuit in Chicago upheld the verdict and the injunction in 2001, and the antiabortion activists appealed to the Supreme Court.

An attorney for abortion rights supporters told the court that upholding the verdict and the injunction would not chill nonviolent protest, but would prevent the authors of a violent campaign of intimidation from escaping unpunished.

"We ask the court not to turn the clock back on 50 years of [anti-racketeering] law," Fay Clayton, an attorney for the National Organization for Women (NOW), told the court.

As it comes to the court, the case turns on issues of federal statutory law; the court rejected the protesters' appeal based on the First Amendment to the Constitution. Englert argued yesterday that the 7th Circuit misread extortion law when it ruled that denying doctors and patients access to the clinics was equivalent to forcing them to hand over their property. And Englert said the lower court misread racketeering law by giving private parties such as the clinics a right to ask a federal judge for an order barring further protests.

But with demonstrators from both sides of the abortion debate pacing near the imposing white steps of the Supreme Court, and with issues of political speech clearly, if indirectly, implicated, all the elements of an emotional confrontation were in place.

The Supreme Court upheld the use of anti-racketeering laws against the antiabortion activists in 1994, ruling that the statutes could be applied even to groups that act out of non-economic motives. The laws were particularly potent because they permit plaintiffs to sue for treble damages.

That year, however, Congress passed a law that makes a repeat of the most aggressive antiabortion demonstrations unlikely. The Freedom of Access to Clinic Entrances Act (FACE) specifically bans the use of force, threats or blockades to interfere with access to reproductive health care, including abortions.

Looking ahead, a victory for NOW could empower institutions facing aggressive protests by advocates of non-abortion-related causes, such as animal rights groups or anti-globalization activists, to deal with the protesters essentially as gangsters.

They could sue in federal court under the Racketeer Influenced and Corrupt Organizations Act (RICO), alleging that the protesters committed extortion under the Hobbs Act, which makes it a federal crime to coerce someone into giving up his or her property if that obstructs interstate commerce. They could also ask a federal judge to order the protesters to cease operating nationwide.

Representing the federal government, Solicitor General Theodore B. Olson told the court that it should uphold the 7th Circuit's broad interpretation of extortion, saying the protesters had disrupted the clinics' right to control their businesses, which, he said, "is a well-recognized and longstanding right of property."

He agreed with the protesters, however, that the clinics, as private parties, could not seek a court order against them; RICO reserves that power for the attorney general, Olson said.

Several justices seemed troubled that defining the antiabortion protesters' conduct in this case -- which even the protesters concede violated various state laws -- as federal extortion might place too powerful a legal club in the hands of those who may want to eliminate controversial but sincere civil disobedience.

"I'm rather concerned about this problem," Justice Stephen G. Breyer said.

"This threatens to bring us constantly into the difficult situation where we have to figure out whether the definition sails too close to the wind for First Amendment purposes," Justice Antonin Scalia said.

Clayton said the key distinction was whether protesters used violence -- which, she said, the antiabortion protesters did, but the civil rights protesters of the 1960s did not.

"If NOW went down to the Augusta National Golf Club to tear up the greens and said they wouldn't stop until the club admitted a woman, they'd be violating the Hobbs Act," Clayton argued.

Clayton seemed to win a measure of sympathy from Justice Sandra Day O'Connor, who interrupted Englert to remind him that "in some cases there were assaults," so "to paint a picture that what we're talking about is pure speech . . . that is not the case."

Englert insisted throughout the argument that his clients could not deny having broken laws against trespassing and other offenses, but that their actions did not rise to the level of extortion because they had not actually taken property.

Englert noted that "activists of all stripes" were supporting his clients in friend-of-the-court briefs, including such groups as People for the Ethical Treatment of Animals, which has staged aggressive protests at fast-food restaurants, and School of the Americas Watch, which has been involved in demonstrations against U.S. foreign policy.

A decision in the cases, Scheidler v. NOW, No. 01-1118, and Operation Rescue v. NOW, No. 01-1119, which have been consolidated, is expected by the end of June.

As the Supreme Court heard a case centered on abortion protests and racketeering law, police officer Girard Fox told a protester outside that his sign's wire handle violated regulations.