In 2001, shortly before Michael Bloomberg became a candidate for mayor of New York, an interviewer asked him if he'd ever smoked marijuana. "You bet I did," he said, "and I enjoyed it."

Yet as mayor, Bloomberg has presided over what a recent report from the New York Civil Liberties Union (NYCLU) calls a "marijuana arrest crusade," seeking to punish pot smokers for an activity he enjoyed with impunity. This little-noticed crackdown, which began under Rudy Giuliani, has disproportionately affected young black and Hispanic men, engendering resentment, distrust of the police and disrespect for the law.

While marijuana arrests have risen between two- and three-fold nationwide since 1990, the increase in New York has been much more dramatic. "From 1997 to 2006," sociologist Harry Levine and drug policy activist Deborah Small note in the NYCLU report, "the New York City Police Department arrested and jailed more than 353,000 people simply for possessing small amounts of marijuana. This was 11 times more marijuana arrests than in the previous decade."

Based on their analysis of arrest data and their interviews with police, arrestees and public defenders, Levine and Small conclude that the pot busts are largely a byproduct of the NYPD's aggressive "stop and frisk" tactics. The U.S. Supreme Court has ruled that police may briefly detain people they suspect of involvement in criminal activity and, as a precautionary measure, pat them down for weapons. Taking advantage of this Fourth Amendment loophole, New York City police stopped and frisked people more than half a million times in 2006.

In the vast majority of cases, these stops do not result in arrests. But sometimes people are carrying small amounts of marijuana. Since police cannot legally search for drugs without probable cause, Levine and Small found, they typically trick or intimidate people into revealing their pot, at which point they can be arrested.

Such trickery not only exposes the contraband; it changes the nature of the offense. Under state law merely possessing a small amount of marijuana (up to 25 grams, about seven-eighths of an ounce) is a citable offense similar to a traffic violation. But having marijuana "in public view" is a misdemeanor.

The NYPD makes about 35,000 such arrests each year. Although marijuana possession is either the only or the most serious charge in these cases, the arrestees are nevertheless handcuffed and taken to a police station, where they are fingerprinted and photographed, and they usually spend a night in jail, an uncomfortable, degrading and often frightening experience.

Contrary to what you might expect, Levine and Small found that people arrested for marijuana possession in New York generally are not smoking pot in public. "Before being approached by the police," they note, "most people arrested for misdemeanor marijuana possession were actually not guilty of what they were charged with."

Why do police waste time and resources manufacturing crimes? Levine and Small note that busting pot smokers is a relatively safe and easy way to pad arrest figures, which creates the illusion of productivity, and generate overtime pay, a practice known as "collars for dollars."

From the collars' perspective, getting arrested for a trivial, victimless offense, which saddles them with criminal records that can impair their ability to obtain an education and make a living, is humiliating and embittering. It is especially rankling because police seem to be targeting poor black and Hispanic men for treatment that would never be tolerated if it were aimed at affluent white New Yorkers.

Survey data indicate that among 18-to-25-year-olds, the age group where the pot busts are concentrated, whites are more likely than blacks or Hispanics to smoke marijuana. Yet Levine and Small found that in New York, blacks and Hispanics are, respectively, five and three times as likely to be arrested for marijuana possession.

For pot smokers caught in the NYPD's dragnet, is Bloomberg's position on marijuana -- "I enjoyed it; you'd better not" -- hard to accept? You bet it is.