Colourful Internet entrepreneur Kim Dotcom and three of his colleagues can be extradited to the US to face criminal copyright charges, a New Zealand judge ruled.
Dotcom's lawyers said they will appeal against the decision.
Judge Nevin Dawson's ruling came nearly four years after US authorities shut down Dotcom's file-sharing website Megaupload, which was once one of the Internet's most popular sites.
Prosecutors say it raked in at least £117 million, mainly from people using it to illegally download movies.
The US has charged the men with conspiracy to commit copyright infringement, racketeering and money laundering. If found guilty, they could face decades in jail.
Judge Dawson presided over a nine-week extradition hearing in which lawyers outlined the case against the four men.
In his ruling, the judge wrote: "The overwhelming preponderance of evidence ... establishes a prima facie case to answer for all respondents on each of the counts."
The judge was required only to decide whether the US had a valid case and not on whether he thought they were guilty or innocent.
The case could have broader implications for Internet copyright rules.
Dotcom's lawyer Ron Mansfield said earlier that if the US side prevailed, websites from YouTube to Facebook would need to more carefully police their content.
The case also raises questions about how far US jurisdiction extends in an age when the Internet has erased many traditional borders. Dotcom says he has never set foot in the US.
"Justice was not served today," said Ira Rothken, one of Dotcom's lawyers.
He said he looked forward to having the decision reviewed in court.
New Zealand justice minister Amy Adams is required to sign-off on any extraditions.
She said today that she would wait for the conclusion of any appeals before making a final decision.
As well as Dotcom, who founded Megaupload and was its majority shareholder, the US is also seeking to extradite former Megaupload officers Mathias Ortmann, Bram van der Kolk and Finn Batato.
The men remained free on bail after the ruling pending their appeals.
Before the ruling, Dotcom wrote on Twitter: "This is my weirdest Xmas ever."