A Superior Court judge ruled yesterday that the D.C. City Council had exceeded its home rule authority by twice using emergency legislation to create a moratorium on condominium conversions.

Judge George H. Revercomb prohibited the city from enforcing the five-month-old ban but delayed the effect of his ruling until Monday to allow the city time to argue whether the conversion law should be enforced while the city appeals Revercomb's ruling.

City Corporation Counsel Judith Rogers said yesterday that Revercomb's ruling potentially could affect how the city uses emergency legislation in areas other than housing.

Revercomb, in a 16-page decision, held that the City Council overstepped its congressional authority by repeatedly invoking "emergency" powers to control the city's condominium market.

"The court concludes that the sucessive enactment of substantially the same substantive provision of law through the emergency power . . . is unlawful," Revercomb wrote.

Revercomb's decision was handed down in response to an Aug. 20 suit filed by the Washington Home Ownership Council, which had asked the court to invalidate the condominium moratorium.

The Home Rule Charter permits the Council to pass emergency legislation effective for 90 days without the usual consent from Congres. On numerous occasions and for a varity of reasons, emergency legislation has been extended again and again.

In some instances, permanent legislation -- legislation that undergoes the congressional consent process -- eventually supersedes the emergency law. In other instances, such as that ruled on by the judge yesterday, no such permanent law is enacted.

The real estate industry has consistently complained that the Council enacts special housing legislation based more on emotionalism and tenant demands than facts and investigation.

The Washington Home Ownership Council suit specifically challenged extensions of several pieces of emergency legislation dealing with housing, including prohibitions on the conversion of apartments to condominiums and cooperatives, as well as amendments guaranteeing tenants first right of refusal in any sale of their apartment buildings.

The moratorium on condominium and cooperative conversions, originally passed on May 22, was reenacted on July 31, and will expire early next month. A special emergency commission set up to study the issue recently made its recommendations concerning permanent legislation to the City Council.

"I feel very stongly that this decision is absolutely in the best interests of the city," said G. V. (Mike) Brenneman, a condominium specialist and director of the Washington Home Ownership Council."You can't have any city run by emergency legislation without any kind of input from anybody. That's no democracy."

Brenneman, as did others, said the decision was "far more wide-reaching than just housing." It goes to the heart of the city's use of its emergency powers, he said. "It's been an abuse that nobody saw fit to challenge over the years . . .The conversions was just the catalytic thing that brought it all together."

"The emergency legislative authority of the Council," Revercomb wrote, "May properly be invoked only where two thirds of the members of the Council find that circumstances exist constituting an unforeseen occurrence or condition calling for immediate action to preserve the public peace, health, safety, welfare or morals."

"On first brush," corporation counsel Rogers said, "it appears that the judge's ruling, wile it is just one judge in one case, set some standards for what constitutes an emergency, limiting it to situations of exigency, crisis situations. He is defining for the City Council what an emergency is."