The Supreme Court ruled Tuesday that states may use anti-racketeering laws to fight pornography but invoked free-speech rights to ban states from seizing before trial the contents of adult bookstores.

The justices threw out an obscenity conviction against a Fort Wayne, Ind., bookstore because authorities seized its contents before trial. But by a 6-3 vote, the justices said prosecutors still may use the state's anti-racketeering law to renew the case.Justice Byron R. White, writing for the court, said the Constitution's free-speech protections do not bar states from using alleged acts of obscenity as a basis for an anti-racketeering law.

"Given that the (anti-racketeering) statute totally encompasses the obscenity law, if the latter is not unconstitutionally vague, the former cannot be vague either," White said.

In other matters acted on Tuesday the court:

- Allowed Kentucky to begin enforcing a 1986 abortion law that includes provisions for parental notification.

- Rejected a constitutional attack on a Texas seat belt law, letting stand a $35 fine against a Houston lawyer for not buckling up.

- Let stand rulings that the public has no right to attend so-called "summary jury trials" held in some legal disputes. Three Ohio newspapers had sought to force such proceedings to be held in open court.

- Agreed to referee a dispute between the U.S. government and American businesses over whether firms receiving money because of claims against Iran must pay part of the money to the U. S. government.

Indiana's Racketeer Influenced and Corrupt Organizations Act is patterned after the much-used federal act that bears the same acronym, RICO. States with RICO laws similar to Indiana's include Arizona, California, Colorado, Connecticut, Delaware, Florida, Georgia, Hawaii, Idaho, New Jersey, North Dakota, New York, North Carolina, Ohio, Oregon, Rhode Island, Utah, Washington and Wisconsin.

White said the Indiana law went too far in permitting prosecutors to padlock adult bookstores before obscenity trials.

While the Constitution generally permits seizure of suspected contraband material, White said, "It is otherwise when materials presumptively protected by the First Amendment are involved."

In a dissent, Justices John Paul Stevens, William J. Brennan and Thurgood Marshall said the obscenity charges against Fort Wayne Books Inc. should be thrown out.

The law allows prosecutors "to cast wide nets and seize . . . the obscene, those non-obscene yet sexually explicit (items), even those devoid of sexual reference," Stevens said.