The Commerce Department, in the first case of its kind before an administrative law judge, yesterday fined a Houston-based subsidiary of a Japanese firm $91,000 for violating antiboycott regulations.

Kintetsu World Express U.S.A. Inc. refused the usual route in antiboycott cases of signing a consent decree and first asked to be heard by an administrative law judge, then appealed that decision to an assistant Commerce Department secretary, who ruled against the firm.

An attorney for the firm said the company did not want to comment on the case, and it was studying it..

Export Administration regulations prohibit American firms from furnishing information to other countries about their business relationships with boycotted or blacklisted countries..

Companies are also required to tell Commerce officials when countries have made boycott requests.

Kintetsu, a freight forwarder, was found guilty of complying with requests for information on 19 different shipments of oil-drilling equipment from its Houston office to Kuwait and Egypt, Commerce officials said. At seven other times, the firm failed to report to the Commerce Department that boycott requests had been made by those same countries on shipments of similar equipment, the officials said.

The Commerce Department had asked Kintetsu to settle the 26 violations for $500 each, officials said. The firm then asked for a hearing before an administrative law judge. The judge, following a hearing, fined the firm $5,000 for each violation, which amounted to $130,000. But the company appealed that decision to Assistant Commerce Secretary Lawrence J. Brady, who yesterday imposed the $91,000 fine, Commerce officials said. The fine was $3,500 for each of 26 violations