THREATS AND RESPONSES: LAW ENFORCEMENT; Rules Eased for Surveillance of New York Groups

A federal judge in Manhattan, citing what he called ''fundamental changes in the threats to public security,'' agreed to modify a longstanding court order that had restricted the New York Police Department's ability to conduct surveillance of political groups.

The police had argued that the restrictions were making it hard to look into terrorism, because they required evidence of a crime to initiate an investigation. That requirement is being relaxed, to allow greater flexibility for the police. The original rules were imposed as part of a 1985 consent decree, the Handschu agreement, which was named for the first listed plaintiff in a 1971 lawsuit over harassment of political advocacy groups by the department's so-called Red Squad.

But the judge, Charles S. Haight Jr. of Federal District Court, left in place a three-member oversight board that can investigate specific complaints in which people contend that police investigations into their political activities violate their rights. ''The Constitution's protections are unchanging,'' Judge Haight wrote, ''but the nature of public peril can change with dramatic speed, as recent events show.'' The guidelines, he said, ''addressed different perils in a different time.''

The judge said he had reached his decision that the police were entitled to a change in the rules ''mindful of the crucial importance of preserving both individual freedoms and public safety, and balancing the legitimate demands of those two goals.''

City and police officials strongly praised the ruling, while lawyers for the group that won the original restrictions said they were disappointed and wanted to see how the city would implement the judge's ruling.

Police Commissioner Raymond W. Kelly, echoing the judge's comments, said: ''We live in a different, more dangerous time than when the consent decree was approved in 1985. This ruling removes restrictions from a bygone era, and will allow us to more effectively carry out counterterrorism investigations.''

Jethro M. Eisenstein, one of the lawyers for the plaintiffs in the long-running case, called the decision ''a major, major loss.''

''What's wrong with this decision,'' Mr. Eisenstein said, ''is that it eliminates a process that became part of the culture of the Police Department. The city, in its effort to get out from under Handschu, portrayed the rules as much more onerous than they were.''

The judge made clear that a central factor in his decision was the Police Department's willingness late in the case to adopt a version of F.B.I. surveillance guidelines issued last year by Attorney General John Ashcroft in the aftermath of the terror attacks.

Judge Haight noted that the F.B.I.'s guidelines ran 24 pages, typed and single-spaced, while the city's first proposal was just over two double-spaced pages, ''the most prominent verb being 'deleted.' ''

He also cited an affidavit filed in the case last month by David Cohen, the department's deputy commissioner for intelligence and a former senior official of the C.I.A. ''In my view,'' Mr. Cohen wrote, ''the N.Y.P.D. would be able to investigate terrorism under the attorney general's guidelines.''

Mr. Cohen had provided the judge with a detailed affidavit laying out the ''changed circumstances'' that warranted the changes. He asserted, for example, that American mosques were largely radicalized, and had been used, along with Islamic institutes, ''to shield the work of terrorists from law enforcement scrutiny by taking advantage of restrictions on the investigation of First Amendment activity.''

Judge Haight said he believed that the continuing existence of the oversight panel, consisting of two senior police officials and a civilian appointed by the mayor, would act as a deterrent to illegal police conduct.

But lawyers for the plaintiffs opposed modifying the original agreement, saying the changes would be fundamental. Mr. Eisenstein cited, for example, one original requirement that officers articulate in writing the basis for investigating a person involved in political activity.

''What was so valuable about Handschu was the investigative discipline,'' Mr. Eisenstein said. ''The process of going through that day in and day out was always, in our view, an incredibly important part.''

Gail Donoghue, special assistant to the city's corporation counsel, said officers were hampered by the requirements. ''There were viable leads that we felt we should have investigated that we could not,'' she said. ''People in the city should be very happy about this.''