A Middlesex Superior Court justice yesterday upheld a controversial Cambridge ordinance which attempts to slow the rate of condominium conversion in the city.

Judge Robert Mulkern's seven-page opinion upheld both the city's right to enact the law, which requires developers to obtain a permit before converting apartments to condominiums or demolishing the units, and the constitutionality of the statute.

"This is terrific news for Cambridge residents, especially tenants," City Councilor David Sullivan, who drafted the ordinance, said last night. "It guarantees tenants protection from unwarranted conversions," he added.

Lawyers for the real estate developers and landlords who challenged the law were unavailable for comment last night. William Walsh, a local attorney who worked with the plaintiffs in the case, said two weeks ago that an appeal was likely if the law was upheld.

"At the very least, this means protection for a year or more--that is how long an appeal would take. And I am confident that it will be upheld on appeal," Sullivan said.

The plaintiffs challenged both the city's right to pass the law with no state approval and the constitutionality of the statute at a hearing two weeks ago before Mulkern.

"I found that the ordinance as drafted was the least restrictive means of obtaining the desired end," Mulkern said last night. He added that the hearing process established by the law ensured that property was not confiscated unfairly.

The ordinance, passed by the City Council August 13, 1979, requires the city's rent control board to hear applications for removal permits. The statute instructs the board to consider the city's "housing emergency" and the hardship of conversion to individual tenants in its decision.

The council passed the law after a study showed that nearly 2000 of the city's apartments had been converted to condominiums since 1975.

At the April 29 hearing, attorneys for the plaintiff called the law a "mammoth piece of legislation...awesome in its magnitude," and complained that the statute deprived owners of the right to dispose of their property as they wished.

City Attorney Stephen Deutsch, arguing in favor of the ordinance at the hearing, said state home rule legislation and the city's own rent control statute gave Cambridge power to regulate condominium conversion.

The rent board granted several permits in early tests of the law last winter, but in the last few months it has denied most of the permits requested.

Only one of the landowners denied a removal permit is currently appealing, but Sullivan predicted last night that other developers might also appeal individual cases now that the law has been upheld.

Harvard is currently seeking a removal permit for an apartment building it owns at 7 Summer Road