Congratulations are in order for Commissioner Kelly and his colleagues in the New York Police Department following the disclosure, by the New York Times, that police officers have been working in plain clothes in midst of protests in the city. Talk about a thankless task and you talk about schlepping up and down the avenues in the midst of a bunch of anti-war protesters. These plain clothes officers risk being surrounded by people holding signs attacking Israel and the Zionists or calling the president of America a Nazi. The officers know that, while most of the protesters are decent and patriotic dissenters, some are pickpockets, some are trouble-makers, and some may even be enemy agents carrying out a strategy that includes a political dimension to a global war. By our lights, we ought to give the NYPD officers onerous duty pay.

We grasp that the Times is not exactly animated by admiration for the work of our officers. The police said yesterday that the paper “confused plainclothes officers used to prevent and respond to acts of violence and other unlawful activity with undercover officers who conduct intelligence investigations under court-approved guidelines.” But our sense is that most New Yorkers will not lose much sleep over these distinctions. They know the First Amendment prohibits the Congress from passing any law abridging freedom of speech and the right to assemble and petition the government. They know it doesn’t say anything about prohibiting policemen from watching an open air protest on public streets and even taking pictures.

Police authority has been dealt with long ago by, among others, the justice after whom our federal courthouse is named. In Socialist Workers Party v. Attorney General, Thurgood Marshall refused, in 1974, a political party’s request to enjoin the government from sending undercover agents to a convention. Justice Marshall wrote that, although any government surveillance activity involves a certain amount of playing with fire, “our abhorrence for abuses of governmental investigative authority cannot be permitted to lead to an indiscriminate willingness to enjoin undercover investigation of any nature, whenever a countervailing First Amendment claim is raised.”

In any crowd situation, police face a challenge in understanding what is happening. Plainclothes officers among protesters provide a vantage to observe activity unseen by the uniformed lines at the edges. In-crowd surveillance can actually protect innocent protesters by making it easier for police to see, if and when things go wrong, who is breaking the law. Since September 11, the city has stepped up its attempts to detect activities that could threaten public safety. It even secured from a federal judge a revision of the so-called Handschu consent decree that governs surveillance so that now it is easier for police to monitor activities that appear legal on the surface but that could cover for terrorists or other serious wrongdoers.

The kinds of protests in which police do plainclothes work does not involve only the anti-war protests. But given the nature of warfare in an era of instant global communications, the anti-war protests offer much to think about. One of our heroes, Russell Wiggins, who is now, sadly, gone but who had been editor of the Ellsworth, Maine, American and before that the Washington Post, liked to relate an encounter he had, on a visit to Moscow during the Vietnam war, with a North Vietnamese official, who confronted the American editor with what Stephen Rosenfeld, later editorial page editor of the Post, once wrote was “a sheaf of American newspaper clippings about the American peace movement.” The communist, Mr. Rosenfeld recalled, “told Russ that was how Hanoi intended to win the war.” Russ Wiggins never forgot it, and neither have we. It only takes one or two enemy agents in a crowd to cause real trouble when, say, a president is in town, and it’s nice to know the N.Y.P.D. is on its toes.