In a ruling that limits the scope of Howard County's landmark antidiscrimination law, a county Circuit Court judge declared today that landlords who create "adults-only" apartment buildings and reject rental applicants with children are not engaging in unlawful discrimination.

The ruling, by Circuit Court Judge Guy J. Cicone, came in a challenge of the county's Human Rights Commission's contention that adults-only rental policies at three Ellicott City apartment complexes were discriminatory. The commission maintains that the owners violated county law because they discriminated against rental applicants on the basis of age, sex and marital status.

In a separate ruling with potentially greater implications, U.S. Housing and Urban Development Secretary Samuel R. Pierce Jr. also said last week that the Howard owners' adults-only policy did not violate federal housing laws. A HUD spokesman declined to comment on how the ruling would affect federal housing elsewhere.

Pierce's determination, based on a separate investigation by HUD, was made public today when a Jan. 24 letter written by John J. Kane, HUD regional director of fair housing and equal opportunity, was entered as an exhibit in the case.

The county commission petitioned the county Board of Appeals last April to issue a "cease and desist" order barring the practice, but landlord Michael Rosen, executive vice president of Town and Country Management Corp., filed suit to block the move. The suit was the first legal test of the county's 10-year-old antidiscrimination law, and today's ruling was was hailed as a victory by lawyers representing Rosen.

County officials, however, expressed disappointment in the ruling, saying the judge did not directly address the key issue in the case.

"He did not answer our direct question . . .whether or not age discrimination covers children," said Jean Toomer, executive director of the county's Office of Human Rights. "We think there is some ambiguity there."

"I think it's extremely clear," countered lawyer Marcy M. Hallock, who represented Rosen. "The judge ruled that letting families live in the units we so prescribe is perfectly lawful."

Earlier this month, Rosen changed his policy and opened six of the 42 apartment buildings -- about 100 of his 1,300 units there -- to families. The rest remain for adults only, according to Hallock.

Cicone limited his ruling to the current policy of maintaining separate buildings for families and did not address past practices at the complex, lawyers said.

Attorneys for the county said they have not yet decided whether to appeal the ruling.