State Attorney General Francis B. Burch has asked the U.S. Supreme Court to review a Maryland Court of Appeals ruling in which key parts of the state's obscenity statute were held unconstitutional.

In the brief, Burch said the ruling by the Court of Appeals last December "flatly contradicts Supreme Court precedent both in area of equal protection and obscenity."

The state court ruling was promoted by an appeal filed by a clerk-cashier for an adult book store in Baltimore. The book store employe had been convicted in an obscenity case and fined $500. His appeal claimed that he was denied equal constitutional protection because employes of adult motion picture theaters were protected from prosecution under the state obscenity statute while employes of adult book stores were not.

While the lower Maryland Court of Special Appeals denied his argument, the Court of Appeals, the state's highest court, agreed with the man, holding that there were no "rational bases" for the denial of equal protection.

In the brief filed yesterday, Burch detailed what he called at least seven rational bases for the differing treatment accorded movie and book store employes by the state obscenity law. Among other things, he said, book store employes, unlike movie employes, may direct a customer to more explicit and exotic materials in the place of business and that books, once sold, could be handed over to juveniles.