WASHINGTON (AP) _ The Supreme Court ruled Tuesday that courts in one state generally cannot keep someone from testifying in another state's court, reviving a multimillion-dollar lawsuit against General Motors over a fatal crash.

Ruling unanimously, the justices said the constitutional requirement that state courts honor court judgments in other states does not let a Michigan judge bar a man from testifying in a separate lawsuit in Missouri.

A court in Missouri had ordered GM to pay $11.3 million to the sons of a woman who died in a fiery crash. But a federal appeals court threw out the award because the trial included testimony by a former GM employee who had agreed in a Michigan court settlement not to testify against GM.

The Supreme Court reversed that decision. ``Michigan's power does not reach into a Missouri courtroom to displace the forum's own determination whether to admit or exclude evidence'' in the GM case, Justice Ruth Bader Ginsburg wrote for the court.

Trial lawyers and the consumer group Public Citizen praised the ruling.

``The court told GM and other companies they're just not going to be able to buy the silence of people who have evidence in important cases,'' said Jeffrey White of the Association of Trial Lawyers of America.

But Jan Amundson of the National Association of Manufacturers said the ruling would discourage companies from pursuing settlement negotiations in lawsuits.

A new trial still must be held in the lawsuit filed by the sons of Beverly Garner of Bevier, Mo., who died in 1990 after the Chevrolet S-10 Blazer in which she was riding collided with another vehicle and caught fire. The damage award also had been invalidated for other reasons.

Tuesday's ruling means the new trial can include testimony by former GM employee Ronald Elwell. He earlier had agreed to a Michigan court order barring him from testifying in lawsuits against GM, and an appeals court cited that order in ruling he should not have testified in the Missouri case.

The Constitution requires courts in one state to give ``full faith and credit'' to court actions in other states.

But the justices said that rule did not allow the Michigan court to bar testimony in a lawsuit filed in Missouri by people who were not involved in the Michigan case.

``Michigan has no power over those parties,'' Ginsburg wrote. ``Michigan lacks authority to control courts elsewhere by precluding them ... from determining for themselves what witnesses are competent to testify and what evidence is relevant and admissible.''

The Michigan order does have the nationwide effect of barring GM and Elwell from suing each other again over the same issues, Ginsburg said.

And, she said, Michigan could bar Elwell from volunteering his testimony although it could not shield him from another state court's subpoena power. She noted that the Michigan settlement agreement said that if another court ordered Elwell to testify, GM would not accuse him of violating the agreement.

Ginsburg said Tuesday's ruling ``creates no general exception'' to the full faith and credit rule, adding that state courts cannot refuse to honor other state courts' judgments for policy reasons.

``But a Michigan decree cannot command obedience elsewhere on a matter the Michigan court lacks authority to resolve,'' she wrote.

The full faith and credit issue often is raised in property disputes and family law cases, such as child custody, where courts in one state may issue orders affecting people in other states.

Also, the Supreme Court one day may be asked to decide whether states must recognize homosexual marriages if one state should legalize them.

Evan Wolfson, a lawyer for the Lambda Legal Defense and Education Fund, said that while Tuesday's ruling did not address the gay marriage issue, he was encouraged by the court's statement that state courts cannot refuse for policy reasons to honor rulings in other states.