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. The decision cannot be appealed.
In the United States, the court's ruling would clash with the First Amendment. But the decision heightens a growing uneasiness everywhere over the Internet's ability to persistently define people against their will.
"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.
Young people, in particular, do not want their drunken pictures to follow them for the next 30 years. "If you're always tied to the past, it's difficult to grow, to change," Mr. Mayer-Schönberger said. "Do we want to go into a world where we largely undo forgetting?"
Read MoreGoogle Glassresumes sales in the US
The court said search engines were not simply dumb pipes, but 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.
Left unclarified was exactly what history remains relevant. Should a businessman be able to expunge a link to his bankruptcy a decade ago? Could a would-be politician get a drunken-driving arrest removed by calling it a youthful folly?
The burden of fulfilling the court's directives will fall largely on Google, which is by far the dominant search engine in Europe. It has more than 90 percent of the search business in France and Germany.
Google said in a statement that the ruling was "disappointing" and that the company was "very surprised" it differed so much from a preliminary verdict last year that was largely in its favor.
Read MoreWhite House wades cautiously into effort to protect onlineprivacy
The decision leaves many questions unanswered. Among them is whether information would be dropped only on Google sites in individual countries, or whether it would be also erased from Google.com. Even as Europe has largely erased its internal physical borders, the ruling could impose digital borders.
Another open question is how much effort a search engine should reasonably spend investigating complaints.
"I expect the default action by search engines will be to take down information," said Orla Lynskey, a lecturer in law at the London School of Economics.
A trade group for information technology companies said the court's decision posed a threat to free expression.
"This ruling opens the door to large-scale private censorship in Europe," said James Waterworth, the head of the Brussels office for the Computer and Communications Industry Association, which counts Facebook, Microsoft and Google among its members. "While the ruling likely means to offer protections, our concern is it could also be misused by politicians or others with something to hide."
Read MoreWhen'liking' a brand online voids the right tosue
That view was echoed by Big Brother Watch, a London-based civil liberties group that was perhaps the first to invoke the specter of Orwell.
"The principle that you have a right to be forgotten is a laudable one, but it was never intended to be a way for people to rewrite history," said Emma Carr, the organization's acting director.
Mr. Mayer-Schönberger, the author of "Delete: The Virtue of Forgetting in the Digital Age," said such concerns were overblown. He said the court was simply affirming what had been standard European practice.