WASHINGTON, March 25 (Reuters) - The U.S. Supreme Court ruled on Wednesday Cox Communications cannot be held liable for piracy by its internet service subscribers of songs owned by Sony Music, Warner Music Group ( WMG ), Universal Music Group and other labels, ending their billion-dollar-plus music copyright lawsuit.

The 9-0 ruling overturned a lower court's decision to order a new trial to determine how much the internet service provider owed the record labels for a form of liability called contributory copyright infringement. Cox had said a retrial could have produced a verdict against the Atlanta-based ISP of as much as $1.5 billion.

More than 50 labels joined together to sue Cox in 2018. Internet service providers like Cox are generally not considered liable under U.S. law for infringement by their users if they take reasonable measures to address it. But the labels accused Cox, the largest unit of privately owned Cox Enterprises, of failing to respond to thousands of infringement notices, cut off internet access for repeat infringers or take other piracy-deterrence steps.

A jury in Alexandria, Virginia, in 2019 found that Cox owed the labels $1 billion for user infringement of more than 10,000 copyrights. The jury found Cox liable both for contributory infringement and vicarious infringement, two forms of secondary copyright infringement liability.

The Richmond, Virginia-based 4th U.S. Circuit Court of Appeals threw out the damages award in 2024. The 4th Circuit ordered a retrial on the award's size after affirming the jury's finding of contributory infringement but reversing its finding of vicarious liability.

Contributory infringement involves holding parties liable for someone else's infringement because they knew about it and contributed to it. Vicarious infringement involves holding parties liable for someone else's infringement because they had the ability to control the infringement and benefited financially from it.

Cox argued that the position taken by the labels in the case would expand the concept of contributory infringement too broadly. Cox said this stance would threaten to cut off access for thousands of innocent internet users including "entire households, coffee shops, hospitals, universities" and others "merely because some unidentified person was previously alleged to have used the connection to infringe."

The Supreme Court heard arguments in the case in December. A lawyer for President Donald Trump's administration argued in support of Cox. Alphabet's Google, Amazon ( AMZN ), Microsoft ( MSFT ) and other internet-focused tech companies supported Cox in the case. Music, film and book industry trade groups backed the labels.