Oil producers and refiners won't be able to operate service stations in Maryland after July 13.

The State Comptroller's Office said it has adopted regulations implementing the state's retail service station divestiture law, which was opposed by major oil companies and small independent oil firms.

The regulations prohibit oil companies from operating the retail stations with company personnel, subsidiary companies, commissioned agents or under a fee arrangement. The companies, however, may continue to own the property.

One area that the major oil companies opposed was the definition of a subsidiary.

The new regulations define it as "a company 15 percent or more of the assets, capital, stock or voting securities of which are held directly by" or controlled by the company. The oil companies, however, said that the usual definition of 50 percent ownership or control should be used.

Goldstein said the definition was designed to provide dealers and jobbers with adequate sources of financing, yet prevent major oil companies from exerting undue control over them.

Maryland was the first state to pass such a law, but was followed closely by the District, Virginia and 35 other states. Maryland's law was passed in 1974 but was challenged in court by some of the major oil companies. On June 13 last year, the U.S. Supreme Court upheld the laws constitutionality.