New Zealand's Court of Appeal has ruled that Internet entrepreneur Kim Dotcom, born Kim Schmitz, is eligible for extradition to the United States.
The German national, who is accused of industrial-scale online piracy, had asked the court to overturn two previous rulings that he and his three co-accused be sent to the US to face charges.
Instead, a panel of three judges backed the FBI-led case, which has dragged on for more than six years.
The saga is widely seen as a test for how far the United States can reach globally to apply American firms' intellectual property rights.
The court said in a statement that: "The evidence relied on by the United States discloses a clear prima facie case to support the allegations that the appellants conspired to, and did, breach copyright wilfully and on a massive scale for commercial gain.
"An extradition hearing is not a trial. It is held to decide whether there is sufficient evidence to commit a person for trial on a qualifying offence."
Mr Dotcom's lawyer Ira Rothken has said his client would appeal the decision in the country's highest judiciary body, the Supreme Court.
The case began in January 2012 when dozens of black-clad police raided his mansion, breaking him out of a safe room and confiscating millions of dollars in cash and property, including a fleet of luxury cars, computers and art work.
US authorities allege Mr Dotcom's creation, Megaupload, netted more than 175 million dollars in criminal proceeds and cost copyright owners more than half-a-billion dollars by offering pirated content, including films and music.
If sent to the US, he will face charges of racketeering, fraud and money laundering carrying jail terms of up to 20 years.