The justices barred Americans from seeking damage awards from cities and government boards that refuse to build wheelchair ramps and make other accommodations for the disabled.
The court said boards and agencies that accept federal money cannot be sued for punitive damages. They can face lawsuits, however, and be forced to pay actual damages and make changes in accommodations.
In another ruling Monday, the justices said that police who want to look for drugs or evidence of other crimes do not have to first inform public transportation passengers of their legal rights.
The ruling gives police guidance on how to approach and search passengers, a case with renewed interest as officers seek out possible terrorists on public transportation.
Justices rejected arguments that passengers, confined to small spaces, might feel coerced.
The loser in the disabilities case was a paraplegic man injured while being taken to jail in Kansas City, Mo. His case was one of four the justices reviewed this year involving the 1990 Americans with Disabilities Act. The other three unsuccessful suits were also brought by people with health problems.
The Supreme Court ruled last year that state workers cannot use the ADA to win money damages for on-the-job discrimination, holding that the disability-rights law does not trump states' constitutional immunity against being sued for damages in federal courts.
This decision shields other agencies, such as local parks and school boards, from money damages.
Jeffrey Gorman, who uses a wheelchair, was injured while being taken to jail in a van after his arrest for trespassing at a country-western bar called Guitar and Cadillacs. He claims officers removed him from his wheelchair, propped him on a bench in the van, and tied him with his belt. During the trip to the jail, he fell and injured his shoulder and back.
Kansas City did not contest the actual and compensatory damages that a jury ordered it to pay for medical costs and lost income, about $1 million. But the city challenged the $1.2 million punitive damage award to Gorman.
Justice Antonin Scalia, writing for the court, said that adding punitive damages in cases like this "could well be disastrous." He said recipients of federal funds probably would not agree "to exposure to such unorthodox and indeterminate liability."
The Supreme Court decided 9-0 to overturn a decision by the 8th U.S. Circuit Court of Appeals in St. Louis, which ruled that Gorman was entitled to punitive damages.
But Justices John Paul Stevens, Ruth Bader Ginsburg and Stephen Breyer said the decision was too broadly written.
The ADA is probably best known for mandating wheelchair ramps and handicapped-equipped bathrooms in public buildings.
Besides Gorman, the court this year also ruled against an assembly line worker with carpal tunnel syndrome, an airline baggage handler with a back injury and a refinery worker with liver disease.
In those cases, the court made it more difficult for workers to demand special treatment when they suffer partial physical disabilities such as carpal tunnel syndrome, that companies' seniority policies almost always trump the demands of disabled employees, and that disabled people cannot demand jobs that would threaten their lives or health.
Justice Sandra Day O'Connor has said the court's current term, which is expected to end next week, probably will be remembered as the "disabilities act term" for the number of cases dealing with the civil rights law.
In the public transportation case, the court ruled 6-3 that police officers in Tallahassee, Fla., were within their rights when they questioned and searched two men aboard a Greyhound bus in 1999.
Justice Anthony M. Kennedy, writing for the majority, said the passengers did not have to be told that they didn't have to cooperate.
Three officers boarded the bus, bound from Fort Lauderdale to Detroit. One officer introduced himself to Christopher Drayton and Clifton Brown, and told them he was looking for illegal drugs and weapons.
He asked to pat down the men's baggy clothing. The men agreed, and officers felt hard objects on the men's legs that turned out to be packets of cocaine.
"It is beyond question that had this encounter occurred on the street, it would be constitutional. The fact that an encounter takes place on a bus does not on its own transform standard police questioning of citizens into an illegal seizure," Kennedy wrote for the court.
Drayton and Brown were convicted and sentenced on drug charges.
The 11th U.S. Circuit Court of Appeals ruled the cocaine should not have been admitted as evidence, because the officers failed to tell the men they were not required to cooperate. That court said the encounter violated the Constitution's ban on unreasonable searches and seizures.
Monday's ruling overturns that decision.
In other Supreme Court rulings: