Washington ? Car buyers beware: People misled about auto loans cannot use a federal law to receive significant damages, the Supreme Court said Tuesday.

When Congress passed the Truth in Lending Act 36 years ago, it decided to let consumers sue dishonest lenders for damages of $100 to $1,000 — a law that has been revised several times since then, but Tuesday’s 8-1 Supreme Court ruling means that the damage caps remain.

The case was watched closely by consumer groups because of its potentially sweeping impact. About 45 million cars are bought and sold in the United States each year. Many are financed through banks or other lenders.

Tuesday’s ruling also applies to other financed purchases, such as appliances and furniture, but not to homes.

The loser was Bradley Nigh, who alleged that he had been a victim of unscrupulous tactics by a Virginia car dealer when he had tried to buy a used car four years ago.

In 2001, Nigh persuaded a federal jury that the dealer, formerly known as Koons Buick Pontiac GMC Inc., had falsely added a $965 anti-theft device to the purchase price of his car, causing a lender to reject his financing. The jury awarded him more than $24,000.

The high court said, however, that he was entitled to no more than $1,000 under the federal law.

“The lesson for consumers is you’ve got to be careful,” said Richard Rubin of Santa Fe, N.M., attorney for groups like the National Association of Consumer Advocates. “Car dealers and other creditors who are stealing money from people are going to continue to steal because it’s profitable.”

A thousand dollars in 1968 would be equal to about $186 in today’s dollars, he said, arguing that Congress now should reconsider the limit.

A ruling the other way could have led to claims for more than $1 billion in damages nationwide each year, auto dealers and banks said, warning that buyers would have had to pay higher interest rates as a result.

“The alternative would have opened the floodgates to a lot of litigation,” said Washington attorney Roy Englert Jr., who represents banking groups.

He said claims under the law often involved technical violations that caused no harm.

The federal lending act was intended to force details of loans into the open and allow consumers to better evaluate the cost of credit. People still can recover actual damages under the law, but they are not entitled to more than $1,000 just for proving that a lender violated the law.

Justice Ruth Bader Ginsburg, author of the ruling, said that “less-than-meticulous drafting” of an amendment to the law caused confusion.

Interpreting the statute to allow larger damages would lead to an absurd result, she said, because it would cap damages at $2,000 for larger credit deals such as mortgages, but allow unlimited damages for car loans.

In the only dissenting opinion, Justice Antonin Scalia argued that it wasn’t the court’s role to fix Congress’ mistakes in sloppily writing the statute.