THE FBI'S UNDERCOVER operation known as Abscam resulted in jury verdicts criminally convicting one U.S. senator, six members of the House of Representatives, the mayor of Camden, N.J., three members of the city council of Philadelphia, an official of the Immigration and Naturalization Service and an assortment of businessmen and lawyers. Many of those caught in the Abscam net and many observers of the way the thing was concluded believed the FBI had acted unfairly, had, in fact, entrapped the defendants. There were also suspicions about the agency's motives and methods, and allegations that the constitutionally mandated separation of powers had been violated. Eleven juries have rejected these charges when they have been elements of a defense case, but civil libertarians and many members of Congress and others continue to question, or at least to be made uncomfortable by, the methods of the Abscam investigation.

Because of these lingering uncertainties, after the conviction and resignation of Abscam defendant Sen. Harrison Williams (D-N.J.) his colleagues created the Senate Select Committee to Study Law Enforcement Undercover Activities of Components of the Department of Justice. Members were charged with the responsibility to investigate the undercover operation and, in particular, to address the civil liberties questions that had been raised.

Last week, the commission issued its final report. The study represents the work of the dozens of lawyers -- both government and private -- who advised the Senate panel. On the major question of the Abscam investigation in particular, the select committee found that "allegations, made by defendants, by members of the media, and by other Abscam critics, of illegality and of other impropriety in the Abscam investigation are not supported by a preponderance of the evidence." Specifically, "none of the individuals who attended a videotaped meeting with FBI undercover operatives had been targeted by the FBI before his name had been raised by an unwitting middleman" and "none of the Abscam defendants was merely playacting . . . . (E)ach public official who received money directly or indirectly from an undercover agent understood that the payment was a bribe."

Nevertheless, the committee issued a warning: undercover operations do create serious risks to citizens' property, privacy and civil liberties. What is needed is "a system of statutes, guidelines and rules that, avoiding both the tyranny of unchecked crime and the tyranny of unchecked governmental intrusion, provides the public with the optimal balance between effective law enforcement and the preservation and nurturing of civil liberties." Recommendations for administrative and legislative changes are then set forth.

The committee criticized both the supervision of informants and accuracy of record-keeping in the Abscam investigation. It is suggested, therefore, that current FBI guidelines on undercover operations be revised so as to ensure greater control by high-level Bureau officials. Congress should also have an opportunity to review the guidelines and should be kept informed, on an annual basis, of undercover operations that have been completed. The committee also recommends that legislation be enacted to create an affirmative defense of entrapment with clear definitions of its elements.

The select committee has completed its work quickly, quietly and thoroughly. Because it deals with a controversial and vital subject in a thoughtful and practical manner, the committee's report deserves the attention of policy-makers in Congress and in the Department of Justice.