Europe's highest court said Tuesday that people had the right to influence what the world could learn about them through online searches, a ruling that rejected long-established notions about the free flow of information on the Internet.
A search engine like Google should allow online users to be "forgotten" after a certain time by erasing links to Web pages unless there are "particular reasons" not to, the European Court of Justice in Luxembourg said.
The decision underlined the power of search companies to retrieve controversial information while simultaneously placing sharp limits on their ability to do so. Jonathan Zittrain, a law and computer science professor at Harvard, said those who were determined to shape their online personas could in essence have veto power over what they wanted people to know.
"Some will see this as corrupting," he said. "Others will see it as purifying. I think it's a bad solution to a very real problem, which is that everything is now on our permanent records."
In some ways, the court is trying to erase the last 25 years, when people learned to routinely check out online every potential suitor, partner or friend. Under the court's ruling, information would still exist on websites, court documents and online archives of newspapers, but people would not necessarily know it was there.
In the United States, the court's ruling would clash with the First Amendment.
"More and more Internet users want a little of the ephemerality and the forgetfulness of predigital days," said Viktor Mayer-Schönberger, professor of Internet governance at the Oxford Internet Institute.
The court said search engines played an active role as data "controllers" and must be held accountable for the links they provide. Search engines could be compelled to remove links to certain pages, it said, "even when the publication in itself on those pages is lawful."
The court also said that a search engine "as a general rule" should place the right to privacy over the right of the public to find information.
The burden of fulfilling the court's directives will fall largely on Google. Google said in a statement that the ruling was disappointing and that the company was surprised it differed so much from a preliminary verdict last year that was largely in its favor.