In a decision city tenant activists called a strong warning to landlords thinking of converting their apartments to condominiums, a state court this week fined a Cambridge landlord $8,000 for making renovations without a building permit.

The court found Irving Busny guilty of doing substantial renovation on a 9 Ellery St. building without a building permit, which he could not obtain because he had not previously acquired a "removal permit" from the city's rent control board allowing him to take the units off the market.

The removal permit law, adopted last summer, is designed to slow the rate of condominium conversion in the city.

"It shows landlords they can't get away with flouting the law; it's a good sign, an important sign," city councilor David Sullivan, who drafted the removal permit ordinance, said yesterday.

Busny yesterday called the court decision "ridiculous," adding "I'm not guilty of any of the things charged."

Busny contended that he had city permission to perform all the renovations, including painting, sanding and other repairs, and violated the law only by installing a new door frame in an attempt to make the building more secure.

"I apologized--I didn't know the contractor would change the frame," Busny said.

Edward Cunningham, a lawyer for the city who helped prosecute the case, said Busny "performed substantial rehabilitation without a building permit."

"Both the building department and the law department should be commended for their action in helping to enforce the law," Sullivan said, adding that he hoped the court decision would "convince the rent control board that they should do likewise in similar cases."

Although the criminal finding in the case does not specifically instruct Busny to end renovations without a permit, Sullivan said "if he keeps doing it, he can keep being fined."

The removal permit ordinance, adopted in the face of increasing condominium conversions within the city, requires landlords to obtain permission from the city before performing major renovations on an apartment building covered by rent control or converting an apartment from rental to residential housing to some other use.

City landlords, who have termed the law an unconstitutional confiscation of private property, have challenged the law through the state courts. A lower court judge upheld the statute last spring, but the state Supreme Judicial Court will hear argument on the ordinance later this fall, perhaps issuing a ruling by early next year.

Although the apartments in Busny's building are rented to tenants, they are owned as condominiums. "They are owned by investors," Busny said.

But Sullivan charged that the "investors" around the city are actually "renting" some buildings to friends, relatives or business partners.

"They only thing that will trigger the removal permit ordinance is if the landlord takes the unit off the rental market," Sullivan said, adding that landlords attempt to skirt the law by selling the units to "investors" who serve as "dummy owners" for the actual occupants.

"The whole thing can be a sham with no rent money ever changing hands," Sullivan said, adding that the city's next control board should ask a court for injunctions to end the practice