A year ago, when terrorists blew up U.S. embassies in Kenya and Tanzania killing 224 people, 12 of them Americans, it galvanized the U.S. government's security efforts overseas. The domestic terrorism we saw in Los Angeles last week should generate an equally strong response at home.

Buford O. Furrow, who has a history of association with various white-supremacist groups, was charged with attempting to murder three children and two women with an Uzi submachine gun at a Jewish community center there and murdering a Filipino-American letter carrier shortly thereafter. When he surrendered to the FBI, he is reported to have explained that he intended the community center assault as "a wake-up call to America to kill Jews." He also admitted he targeted the postal worker in part because the man was a minority, authorities said.

The Los Angeles shooting came five weeks after a three-day rampage by white supremacist Benjamin Nathaniel Smith, who killed two men and wounded nine others in Illinois and Indiana and then killed himself before police could arrest him. All the victims of Smith's shooting spree were black, Jewish or Asian American.

Events such as these leave a lingering sense of dread. The public places in which we live our common lives seem more vulnerable. Despite the recent shootings, the foundations of religious tolerance in modern American society remain stable. But our open society is prey to misuse by extremist groups, and the health of our civic culture should not inure us to that threat.

Free speech and a largely unrestricted gun trade can be a heady combination for supremacist groups trawling the Internet or elsewhere for recruits. We need to find a response that will not damage the traditional liberties of American society but will keep hate groups from using them as shelter while they swagger and intimidate to win new converts.

What can we do? One useful step would be for the FBI to expand its efforts to keep watch on hate groups and be in a better position to stop crimes before they happen. This will take additional manpower, and resources and Congress should supply the needed funds.

There is some history to overcome here. Civil libertarians raised serious concerns about the tactics employed by J. Edgar Hoover's FBI against civil rights, antiwar and radical groups in the 1960s and '70s. A reaction against those abuses led the Justice Department in the mid-'70s to shut down many of its domestic security operations and adopt an extremely cautious approach in opening new investigations. But now that the FBI has had 20 years to rebuild its reputation for respecting civil liberties, we can seek a restored balance. We should strengthen the bureau's ability to follow the activities of hate-mongering supremacist organizations before they plant a bomb or pull a trigger.

A model already exists in the FBI's approach to foreign counterintelligence and organized crime, where investigators look at the structure of the criminal enterprises themselves, try to anticipate major crimes before they happen and seek, if possible, to capture key members of criminal groups.

The bureau's joint "terrorist task forces" throughout the country, for example, marry the FBI's forensic talents and investigative reach with local police departments' savvy about suspect groups or individuals in their jurisdictions. The aim is to follow a terrorist organization's use of safe houses, false identities, recruitment patterns and illegal purchases of guns and explosives. With that information, law enforcement can be in a position to move in and make arrests or prevent a terrorist act from being carried out.

This sort of investigating requires a substantial commitment of agents, resources and time. I learned just how labor-intensive it can be when, as a federal prosecutor in New York, I worked with the New York FBI terrorist task force in the mid-'80s. The task force's target was a loose group of about 75 people who planned bomb attacks on federal office buildings and other terrorist acts. From a war room in the New York federal building we pursued leads from surveillance sightings, record checks and investigators' interviews with acquaintances. Along the way we accumulated a cache of seized guns and documents, among them one conspirator's graph-paper sketches, done in colored inks and childish handwriting, showing how to construct time-fuses for explosive devices. In the end the task force was able to arrest nearly all of the conspirators.

With hate groups, the investigative challenge is even more formidable than we faced in New York, where we were trying to keep track of a fairly small number of suspects. According to the Southern Poverty Law Center, there are 537 white supremacist and neo-Nazi groups in the United States, and another 435 militia and posse groups.

It is even more daunting to think of keeping track of people like Furrow and Smith, whose associations with these groups could have been traced but whose acts of violence, as far as is known, were planned and committed alone.

Investigating groups that flirt with force and violence is not incompatible with American freedoms. While free speech, even of a loathsome nature, is protected under the First Amendment, law enforcement can't ignore the possible consequences when extremist groups publicly suggest violent plans, or promote violence by others. A group that calls for the killing of Jews should be taken at its word. An extremist group that appears to be planning violence should not be shielded from FBI surveillance just because it sacrilegiously calls itself a church. The fact that racist rhetoric is posted on a public Internet site and may be constitutionally protected speech shouldn't prevent authorities from looking for possible illegal or violent underground activities.

Another subject that needs reexamination is the civil commitment procedure. The tools we give local courts and mental health authorities to evaluate mentally deranged and violent people should be strengthened. A man who indicates that he is thinking about suicide and shooting people, as Furrow is said to have done well before his rampage, should be considered a possible candidate for civil commitment whether or not he has committed a new crime.

In commitment proceedings, at least when the person involved may be a potential hate killer, there should be some procedure for the appropriate authorities to obtain criminal records and any information about gun ownership. That would help determine--more concretely than psychiatric evaluation alone--whether a bigot is just spouting hot air, or is a real threat to others.

Finally, criminal laws concerning threatened violent acts should also be strengthened at the state level. If more than one person is involved, criminal conspiracy laws can be used, since once there is an agreement to commit a crime, any overt act--even one as trivial as purchasing a road map--can trigger prosecution even if no victim has been selected. However, there is no such powerful legal tool against nuts who act alone. A prosecution for an attempted offense is possible only when a criminal plan is well along, and a criminal threat can generally be prosecuted only when a particular victim has been targeted.

It may be possible to find a way to apply the principle of conspiracy laws to a lone plotter--that is, once a decision to commit a crime has been made, any action on that decision can trigger prosecution. Then, if there's evidence that an extremist is planning violence against another ethnic or religious group and he commits even a minor act in pursuit of that plan, the law could nab him.

The street smarts of the Secret Service may hold a lesson here. To deter real threats to the president's life, Secret Service agents have long sought out and interviewed anyone who speaks of using violence against the president, even when the statement may have been uttered in jest or in a moment of anger. These interviews allow the agents to evaluate the threat at closer hand, and let them take precautions if the threat seems serious. Are we sure that threats against racial and religious groups cannot be equally serious?

We are vigorous in rooting out terrorism abroad. Domestic tranquillity is just as important. The national stalemate over gun control should not keep us from taking steps that are possible in meeting the threat of home-grown extremists.

Ruth Wedgwood is a professor of law at Yale University and a former federal prosecutor in the Southern District of New York. She has also advised the FBI and the Justice Department on investigative guidelines.