The justices' decision returns to a lower court the case of a family of an American college student who was killed in an Islamic State terrorist attack in Paris. The family wants to sue Google for YouTube videos they said helped attract IS recruits and radicalize them. Google owns YouTube.
Google claims immunity from the lawsuit under a 1996 law that generally shields social media company for content posted by others. Lower courts agreed with Google.
The justices had agreed to consider whether the legal shield is too broad. But in arguments in February, several sounded reluctant to weigh in now.
In an unsigned opinion Thursday, the court wrote that it was declining to address the law at issue.
The outcome is, at least for now, a victory for the tech industry, which predicted havoc on the internet if Google lost. But the high court remains free to take up the issue in a later case.
The court also ruled in a separate lawsuit involving Google, Twitter and Facebook, heard on the same day in February, that seeks to hold them liable for a terrorist attack in a Turkish nightclub that killed 39 people.
A lower court allowed the suit to proceed under a law against aiding and abetting terrorism.
The justices' unanimously ruled that case could not go forward.