A lawyer for Kim Dotcom has filed papers with a United States court to dismiss what he calls the "flawed" case against his client.
The German co-founder of the file-sharing site Megaupload is living in New Zealand where he has residency.
He and three other men are facing extradition to the US on charges of internet piracy and money laundering in what is described as the largest criminal copyright case in the world.
Mr Dotcom's American-based lawyer Ira Rothken says US authorities can't legally charge Megaupload, as it is a Hong Kong corporation and does not have a presence in America.
"We're just asking the United States to play by the rules."
Mr Rothken says he is confident that the charges will be dropped.
However, if the court does not accept the argument, Mr Rothken says he has filed papers to request that Mr Dotcom and his co-accused get access to their frozen funds so they can pay for their legal defence.
Megaupload was indicted in a federal court in Virginia on 19 January this year and the site was shut down. Mr Dotcom and his co-accused were arrested in Auckland the following day.
Formal papers requesting their extradition were lodged in early March.