TEN YEARS AGO, the District twice launched an effort to put a curfew law for juveniles on the books. Officials would have made it illegal for those 18 and younger to be on the city streets between 11 p.m. and 6 a.m. on weeknights and between midnight and 6 a.m. on weekends, except in connection with "legitimate" employment or unless they had documents showing good reason to be on the streets. Both efforts failed to pass judicial muster. Undeterred, the city began enforcing a new curfew law last night.

Old concerns remain. The new statute, which was upheld by the D.C. Circuit Court of Appeals in June, is a lot like the old laws rejected by U.S. District Judge Charles Richey in 1989. Under today's rules, juveniles can't be outdoors from 11 p.m. to 6 a.m. Sunday through Thursday, and from midnight on weekends, without adult supervision. This time the cutoff is age 16 rather than 18. And the law holds parents and guardians more accountable, subjecting them to fines and other sanctions for youth curfew violations. As with the old law, this ordinance also contains exceptions for emergencies, travel to and from work, parent-approved errands and attendance at chaperoned school events.

The passage of a decade hasn't changed the fact that the curfew law, as Judge Richey explained in 1989, "subjects the District's juveniles to virtual house arrest each night." True, minors don't have the same constitutional rights adults do. But the freedom of movement of law-abiding youths has been curbed as a result of this new law. There are added concerns. Will the curfew compound problems for a Metropolitan Police Department already feared missing in action in certain communities? Children caught violating the new law will be taken to station houses or, if under 12, to the D.C. Department of Child and Family Services. Will that divert already scarce police officers from street patrols? Will enforcement of the curfew depend upon the neighborhood?

Advocates expect the law to have a positive effect on juvenile crime rates. Let's hope that occurs. The way in which the law is enforced bears close watching.