A D.C. Superior Court judge has ordered the city to stop filing criminal charges against underage drinkers, ruling that possession of alcohol by a minor is a civil infraction under city law.

The decision by Judge Zoe Bush was a victory for lawyers representing dozens of people who have been charged with underage possession of alcohol, only to have their cases thrown out because various judges found that criminal charges were unwarranted.

Police and prosecutors, who had been averaging up to 15 criminal cases a week, said the threat of arrest was a deterrent. But the plaintiffs, many of them college students, said the arrests were unsettling experiences that left them with undeserved criminal records.

Instead of being given citations akin to traffic tickets, as would happen were they charged with a civil violation, the plaintiffs were arrested and taken to police stations, where they were photographed, fingerprinted and often held for several hours.

Bush's action followed rulings in two cases last year by the D.C. Court of Appeals and D.C. Superior Court. They held that under District law, possession of alcohol by a person younger than 21 is a civil offense, punishable only by fines and suspensions of driving privileges. The rulings have led to more than 100 dismissals of criminal cases within the past year.

But city attorneys and the D.C. police have challenged the dismissals, saying they were based on an interpretation of a law that was changed. They said that revisions were made in the law in 2001 to clarify that underage alcohol possession is a criminal offense.

Elsewhere in the region, the legal consequences of underage possession vary. In Maryland, it is generally treated as a civil offense, according to the state attorney general's office. In Virginia, it is more apt to be handled as a criminal offense, authorities said.

In the District, police and prosecutors had continued, until late Thursday, to bring criminal charges against alleged underage drinkers, often as part of coordinated undercover crackdowns.

The city attorney general's office said Friday that it has stopped filing criminal cases against alleged underage drinkers. The city attorney general, known until this week as the corporation counsel, prosecutes a range of violations of the D.C. code, including public intoxication cases.

David Rubenstein, deputy attorney general for public safety, said the court's ruling took away important leverage for police.

"What happens, by decriminalizing it, is the police lose the ability to use it as a law enforcement tool, and there is a substantially reduced deterrent effect for young people," Rubenstein said.

Bush's ruling, issued last week, is not sitting well with the city's top cop. "I'm certainly not happy about it," Chief Charles H. Ramsey said Friday. "Not being able to enforce the law certainly is a setback."

But city officials have not given up on pursuing criminal action.

An amendment has been proposed to the city's underage drinking statute to address the ambiguities that judges have cited in the law, and the D.C. Council could take up the proposed changes as soon as this week.

It will be another attempt to clarify a law that has prompted a potentially damaging lawsuit against the city and has generated acrimony between the courts and city officials.

The suit, initially filed in federal court and later re-filed in Superior Court, alleges that people arrested on underage possession charges in recent years were subjected to wrongful arrest. It seeks to have their records expunged and damages paid.

Carol Elder Bruce, the attorney who filed the suit, said police and prosecutors want to have the threat of jail and a criminal record at their disposal because they believe it serves as a deterrent -- whether it is legal or not.

"They are deliberately trying to teach these kids a lesson by treating them roughly, by intimidating them and mocking them and making them as uncomfortable as possible," said Bruce, a partner at Tighe Patton Armstrong Teasdale.

The suit, which is seeking class-action status, identified the plaintiffs only as John Doe to spare them further exposure, Bruce said.

"It was embarrassing," said an 18-year-old plaintiff who attends Georgetown University. He said he was arrested on 36th Street NW in front of dozens of schoolmates after a friend he was with was spotted carrying a couple of beers. "The next morning, everyone knew already. It was really embarrassing."

The experience left the 18-year-old disenchanted with the police, said the student, who like the other plaintiffs spoke only on the condition of anonymity. "After that, I really don't trust the Metropolitan Police so much," the student said.

Another plaintiff, a 19-year-old student at George Washington University, was arrested this year. He and a friend were leaving a Foggy Bottom grocery store carrying some beer when they were confronted by an undercover police officer who demanded to know how old they were, he said. Handcuffed to each other, they were taken away and charged with underage possession.

"It was a little surreal," the student said. "It was kind of like a dream, it happened so fast."

The charge was thrown out, but prosecutors have appealed the dismissal, so the student's fate with the law is in limbo.

Staff writers Jamie Stockwell and Del Quentin Wilber contributed to this report.