The law, approved in May, requires sober houses to move to areas zoned for motels or medical centers. The lawsuit alleges that the city is "in essence creating a defined ghetto for persons in recovery" and is trying to push the facilities out of town.

"The ordinance is a sweeping attack aimed at excluding persons in recovery from residing in any residential district in the city," the attorneys wrote in their complaint. "... In effect, the city has segregated from the remainder of the city's residential population those city residents that, due to addiction, require a supportive alcohol- and drug-free environment."

Cities across the nation have tried, often unsuccessfully, to regulate sober houses and other treatment centers by enacting stricter zoning requirements, said Ellen Weber, an assistant professor at the University of Maryland's law school. Legal challenges to such laws often are successful, Weber said, because case law states that regulations can't be passed that effectively preclude such houses from locating in a residential community.

Despite the chances of losing in court, Weber said, cities often enact restrictions anyway.

"One, [the sober houses] don't have the time or the finances to fight it, and two, to the extent that they want to have a healthy environment [for their patients] ... they don't want to put them into an environment where there's a great deal of hostility and stigma," Weber said. "It's a tool to keep people out."

Mayor Steven Abrams said Friday the city did not discriminate against recovering addicts in passing the ordinance. "The city's position all along has been that it's a legitimate regulation under our local zoning authority," said Abrams.