In a 7-2 vote, the court ruled that a federal appeals court in Richmond, Va., wrongly threw out the conviction of Randy Edward Hayes. Justice Ruth Bader Ginsburg wrote the majority opinion. Chief Justice John Roberts and Justice Antonin Scalia dissented.

The federal government, gun control groups and women's rights advocates worried that a ruling for Hayes would have weakened the federal law enacted in 1996 that applied the 40-year-old ban on gun possession by a felon to people convicted of domestic violence misdemeanors.

The 4th U.S. Circuit Court of Appeals ruled in Hayes' favor because the West Virginia state law on battery under which he was convicted did not contain specific wording about a domestic relationship between the offender and the victim.

Nine other appeals courts rejected that interpretation.

The justices, in an order Monday, are refusing to hear FTC's plea to reinstate the commission's ruling that Rambus, based in Los Altos, Calif., violated antitrust law.

A federal appeals court in Washington overturned the FTC ruling last year.

The Bush administration had declined to back the FTC in its appeal to the high court.

Supporters of both Democrat Al Franken and Republican Norm Coleman see a winner influencing the balance of power in the Senate, even as the Democrats already firmly hold the chamber.

"The 59th vote in the Senate is very valuable, and that's obvious now," said Kathryn Pearson, an assistant professor of political science at the University of Minnesota. "It's valuable for Democrats to add a vote, and it would be very valuable to Republicans to deny that vote."

For Democrats, the absence of Franken's vote has already made passing legislation more of a challenge. The $787 billion stimulus bill squeezed through the Senate late Friday night on the vote of Sen. Sherrod Brown, D-Ohio, who was flown back to Washington on a government plane from his home state, where he was mourning the death of his mother. Democratic Sen. Edward M. Kennedy of Massachusetts, who is suffering from a brain tumor, could not attend the vote.

The six-person Broward County jury must decide whether Stuart Hess was addicted to cigarette nicotine before he got lung cancer and died. If so, the jury would later decide any damages against the Philip Morris tobacco company.

The lawsuit by widow Elaine Hess is the first to go to trial since the Florida Supreme Court in 2006 threw out a $145 billion class-action jury award, ruling that each case had to be proven individually.

Hess' lawyers said Thursday he was hopelessly addicted to nicotine. The lawyer for Philip Morris said Hess chose not to quit despite known health risks.

The judges in the cases said the evidence was overwhelmingly contrary to the parents' claims — and backed years of science that found no risk.

"It was abundantly clear that petitioners' theories of causation were speculative and unpersuasive," the court concluded in one of a trio of cases ruled on Thursday.

The ruling, which was anxiously awaited by health authorities, was a blow to families who have filed more than 5,000 claims for compensation through the government's Vaccine Injury Compensation Program. The claims are reviewed by special masters serving on the U.S. Court of Claims.

To win, the families' attorneys had to show that it was more likely than not that the autism symptoms in the children were directly related to a combination of the measles-mumps-rubella shots and other shots that at the time carried a mercury-containing preservative called thimerosal.

But the court concluded that "the weight of scientific research and authority" was "simply more persuasive on nearly every point in contention."

The court still has to rule on separate claims from other families who contend that rather than a specific vaccine combination, the lone culprit could be thimserosal, a preservative that is no longer in most routine children's vaccines. But in Thursday's rulings, the court may have sent a signal on those cases, too:

"The petitioners have failed to demonstrate that thimerosal-containing vaccines can contribute to causing immune dysfunction," a judge wrote about one theory that the families proposed to explain how autism might be linked.

Most juvenile offenders are released when they turn 18, but the extended commitment law allowed the Department of Youth Services to retain custody up to age 21 if a youth posed physical danger.

In unanimously striking down the law, the Supreme Judicial Court said it was unconstitutional because the law "contains no indication of the nature and degree of dangerousness that would justify continued commitment."

The court noted that the Legislature in 1990 had removed language that the danger a youth posed be due to a mental condition.

"The court said we don't lock people up based on an allegation of dangerousness when we don't know what that means," said attorney Barbara Kaban, deputy director of the Children's Law Center of Massachusetts.

She represented the three youths who challenged the law. Kaban said the three had been charged with crimes that included larceny and assault and battery with a dangerous weapon.

All were turned over to the department's custody when they were 16. Each was initially placed on probation, then sent back to a juvenile detention facility after violating the terms of probation at least once. The department filed applications for extended commitment orders for all three shortly before they turned 18.

Jennifer Kritz, a spokeswoman for the Department of Youth Services, said the department is reviewing the court's ruling and expects to be ordered to release about 12 youths being held under the law.