In a nearly four-decade-old case involving how the police investigate political groups, a federal judge ruled this week that New York City unnecessarily allowed a lawsuit to drag on for more than an extra year.

Lawyers for the city failed to notify the plaintiffs that the police directive at the heart of the suit had been replaced, Judge Charles S. Haight Jr. of United States District Court in Manhattan wrote in a decision issued Wednesday. Instead, the city’s lawyers continued to vigorously defend the old directive, Interim Order 47, which gave the Police Department broad discretion to make video recordings of public gatherings, the judge wrote. That order was revoked in April 2007 and replaced by one that restricted video recording to cases in which there is cause to believe that a crime may be committed.

In his ruling on Wednesday, Judge Haight ordered the city to pay the plaintiffs’ legal fees for the nearly one and a half years between the time Order 47 was revoked and September 2008, when the plaintiffs were inadvertently notified of the change. Judge Haight also directed the city to notify the plaintiffs if the subsequent order, Interim Order 22, is modified or replaced.

“I think it plain that corporation counsel’s conduct cannot be excused,” Judge Haight wrote, referring to the law agency that represents the city. “Corporation counsel’s conduct in keeping mum about this event of central importance, and continuing the litigation as if it had not occurred, multiplied the proceedings unnecessarily and therefore unreasonably.”