WASHINGTON — The Supreme Court on Wednesday made it harder for music and movie makers to sue for online piracy, ruling that internet providers are usually not liable for copyright infringement even if they know their users are downloading copyrighted works.

In a 9-0 decision, the justices threw out Sony’s lawsuit and a $1-billion jury verdict against Cox Communications for copyright infringement.

Lower courts upheld the lawsuit against Cox’s internet service for contributing to music piracy, which the company did little to stop.

Sony’s lawyers pointed to hundreds of thousands of instances of Cox customers sharing copyrighted works. Put on notice, Cox did little to stop it, they said.

But the high court said that is not enough to establish liability for copyright infringement, which remains a hot button issue in the music and film industries with the advent of AI tools that have spread the misuse of copyrighted content and sparked lawsuits between studios and AI companies.

“Under our precedents, a company is not liable as a copyright infringer for merely providing a service to the general public with knowledge that it will be used by some to infringe copyrights,” Justice Clarence Thomas wrote for the court.

Two decades ago, the court sided with the music and motion picture producers and ruled against Grokster and Napster on the grounds their software was intended to share copyrighted music and movies.

But on Wednesday, the court said “contributory” copyright infringement did not extend to internet service providers based on the actions of some of their users.

“Cox provided Internet service to its subscribers, but it did not intend for that service to be used to commit copyright infringement,” Thomas said. “Cox neither induced its users’ infringement nor provided a service tailored to infringement.”

Mitch Glazier, the chairman of the Recording Industry Assn. of America, said he was “disappointed” in the court’s ruling, as the case was “based on overwhelming evidence that the company knowingly facilitated theft.”

“To be effective, copyright law must protect creators and markets from harmful infringement and policymakers should look closely at the impact of this ruling,” Glazier said in a statement. “The Court’s decision is narrow, applying only to ‘contributory infringement’ cases involving defendants like Cox that do not themselves copy, host, distribute, or publish infringing material or control or induce such activity.”

Karyn Temple, senior executive vice president for the Motion Picture Assn., said in a statement that the decision “upends the critical legal doctrine of contributory infringement for copyright.” She added: “Unfortunately, the Court’s opinion today ignores this well-established rule and congressional intent, which is particularly disappointing amidst a growing consensus about the need for more accountability for facilitating harmful online conduct, not less.”

In its defense, Cox argued that internet service providers could be bankrupted by huge lawsuits for copyright infringement, which they said they did not cause and could not prevent.

“The decision means that the Supreme Court isn’t coming to the entertainment industry’s rescue,” said attorney Michael K. Friedland. “The copyright infringement problem is a technological problem. The modern internet makes infringement really easy. The decision means that the industry is going to have to solve the problem itself — by developing its own better technology to protect its intellectual property.”

Rachel Landy, who teaches copyright law at Cardozo Law School in New York, said the music industry has no good options and may need to go to Congress.

“The record industry could go after the individual users who share works online without authorization, but that led to suboptimal outcomes in the past: bad publicity and judgment-proof defendants,” Landy said. “And now, the court has narrowed the contributory liability doctrine such that they are also unlikely to get recourse from the deeper pockets. It may be that their best recourse is to go to Congress for a fix.”

The American Civil Liberties Union and the Center for Democracy and Technology joined the case in support of Cox and welcomed the decision.

It is “a win for freedom of speech,” said Samir Jain, a CDT attorney. “If the court hadn’t decided in favor of Cox, it would have turned internet service providers into censorship machines acting on behalf of powerful rights-holders.”

Times staff writer Cerys Davies in Los Angeles contributed to this report.