By Louis Lombardi

Mayor Nutter has decided to take an ironfisted approach to the city's flash-mob problem. Although his motives and much of his response are commendable, his decision to institute a curfew for portions of the city is troubling. While last weekend's relative quiet was attributed to the curfew, its reported effectiveness does not necessarily make it right.

Under the curfew, youths under 18 who are found out and about after 9 p.m. in Center City, the South Street area, and University City are subject to arrest. The problem with this is that it's a "status crime": a crime based not on what people do, but on who they are - in this case, children and adolescents.

America has had plenty of experience with status crimes. The most obnoxious example is the Jim Crow laws of the South, which criminalized people based on the color of their skin. Another example is vagrancy laws, which in effect criminalized homelessness. Such laws were eventually abolished as an affront to constitutional principles.

Although imposing a curfew on young people may not be as offensive as Jim Crow or vagrancy laws, it is nevertheless an extraordinary assertion of government power that dictates where certain people may lawfully be present. How can this be reconciled with our system of government?

Usually, for such an assertion of power to be legitimate, there must be some emergency situation confronting local authorities - think riots and other civil disturbances. Do Philadelphia's flash mobs rise to that level?

True, crimes are being committed and lives are being adversely affected, but there hasn't been the sort of wholesale disorder or full-blown rioting that typically justifies such a drastic remedy. Law enforcement officials have not been overwhelmed by the mobs.

By the standards of this curfew, any group seen as having a propensity to commit crimes can be kept off the streets by simple government decree. If we really want to make the curfew effective, we should apply it to all men ages 16 to 25, as statistics show they account for most of the street crime in America. If there were any way to enforce such a law and defend it from constitutional challenge, Philadelphia's crime problem could be solved in one fell swoop.

Authorities have many options for dealing with mobs short of a curfew. Outreach programs can help discourage them, as does an increased police presence in affected areas. Police must also develop intelligence on the formation of mobs and arrest those involved through good old-fashioned police work. The court system, too, must respond with quick, strong sanctions that send a clear message. It may not be easy, but a coordinated criminal-justice response will go a long way toward ending the flash-mob phenomenon.

The mayor's frustration at the flash mobs and his sense of urgency in dealing with them is widely shared. Lawlessness cannot be tolerated. But it must be confronted in a manner consistent with our Constitution. The curfew is not, and it should be rescinded.

Louis Lombardi is an attorney and

former New York City police captain

who lives in State College. He blogs