The more New Yorkers hear about the lengths the police department went to in order to protect the city during the Republican National Convention, the more appreciative they are going to be. The convention took place not only when enemy agents were searching for opportunities to attack symbols of our democracy but in the wake of violent demonstrations in Seattle, Quebec, and Genoa. A picture of how the New York Police Department moved to prevent a recurrence of that kind of violence here is emerging in a lawsuit on behalf of lawyers for persons arrested during the course of the protests.

It turns out that a full year before the convention, what the New York Times, in a dispatch Sunday, called “teams of undercover New York City police officers” traveled not only across America but to Canada and even Europe to spy on persons who were plotting mayhem in the city. The Sunday Times, citing police records and interviews, reported that the officers “attended meetings of political groups, posing as sympathizers or fellow activists” and “filed daily reports with the department’s Intelligence Division.”

“Our goal,” the department’s deputy commissioner of public information, Paul Browne, told us in an e-mail Saturday, “was to safe guard delegates, demonstrators and the general public alike during the convention, and to make certain that the kind of window smashing and other violence that had erupted in Seattle, Quebec, Genoa and other protest venues did not occur in New York City.” He said: “We wanted to stop protesters from shutting down the financial district, as happened in San Francisco the year before.”

In a few instances, according to Mr. Browne, the police “kept track of individuals who planned to come to New York for the RNC and who had resorted to extreme violence in the past.” One example he cited was of a convicted terrorist named Richard Picariello, who, Mr. Browne said, “had a history of resorting to bombings to express dissent.” According to Mr. Browne, Picariello, despite his public assertions to the contrary, “came to New York for the RNC” and “was photographed in New York by CNN.” Picariello wasn’t arrested during the convention, Mr. Browne said, but “most of those who were resided outside of New York.”

“United for Peace & Justice attracted 800,000 to its march and rally,” Mr. Browne said. “As we anticipated, the vast majority of protesters were peaceful and law-abiding.” Yet another thing to bear in mind is that the protesters weren’t the only ones with First Amendment rights to assemble peaceably. There were also the Republicans. Mr. Browne pointed out that in “the days that followed the main protest, the Police Department stopped smaller groups who tried to prevent delegates from leaving their hotels, who tried to stop delegate buses from reaching [Madison Square Garden], and who had tried to shut down Wall Street during the convention.” That they failed, that the peace was kept, with the arrest of only a few slivers of 1% of the protesters in town, that was the a triumph of one of the great police operations in the city’s history.

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If there’s a large context to all this, it is the relevance to the current war on terror of the so-called Handschu guidelines. Handschu was a legal case that was brought by Barbara Handschu, Abbie Hoffman, and other left-wingers during the Vietnam War. They wanted to prevent the police from making videotapes of political demonstrations. Though the Supreme Court has ruled that surveillance is not a violation of demonstrators’ rights under the First Amendment. Eventually the city, in a historic blunder, entered into a consent decree settling the case, agreeing to guidelines that required evidence of unlawful conduct to be present before an investigation could be undertaken.

In anticipation of the Republican convention, the police department gained — and followed — a modification of the guidelines, which permitted the pursuit of investigative leads. But, in the midst of a war that has already seen thousands killed here, do our police need to be hamstrung by these kinds of guidelines at all? Most of the opposition to this war may be from patriotic Americans acting in good faith. But certainly enemy agents are at large in our city. The last thing we need is to tie the hands of the police in apprehending these spies and agents, uncovering their plans, and bringing them to justice.