The Megaupload accused could be extradited on charges which were not in copyright law if their actions showed they could have breached other laws, the Supreme Court has heard.
Crown lawyer Kieran Raftery, for the United States, argued there were grounds to do so for copyright infringement, particularly in cases where offending was so serious it warranted greater penalties.
One such example was access of a computer for a dishonest purpose to describe the way the Megaupload accused used their own systems in handling copyright-infringing material.
Lawyers for Kim Dotcom, Mathias Ortmann, Bram van der Kolk and Finn Batato have argued the US is bound by the Copyright Act when it comes to aligning its charges with New Zealand law.
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They say the US approach, if enshrined in legal precedent, would have "mums, dads and the kids" potentially facing criminal charges for breaches of copyright.
Instead, they say the way Parliament considered and wrote the Copyright Act shows it intended it to be the legislation which the courts had to consider for cases involving copyright allegations.
The legal argument is seated in legal maneuvering in which lawyers for the Megaupload accused have argued various legal grounds are a barrier to extradition to the US on charges relating to massive alleged copyright violation.
The US, in response, have described multiple avenues by which its says the accused qualify for extradition.
Raftery said there were examples of prosecutions which showed it was possible to prosecute people under alternative laws.
"There are many instances where some conduct can give rise to different charges."
He pointed to United Kingdom cases in which penalties under copyright law were "trivial" yet the scale of offending warranted more serious sentencing options.
Raftery said the primary legislation was the preferred pathway but the courts recognised it was not the only option.
Raftery came under challenge from Justice Susan Glazebrook over the application of the charge a computer system had been used dishonestly.
She asked how it could be dishonest when the computer system being used belonged to the accused.
Raftery said there was a body of evidence showing they were "accessing the material on the computer system which is not theirs, which they don't have authority to use".
He was also quizzed on a point raised by the Megaupload accused - that the US case was said to lack evidence showing the material they were accused of pirating was actually covered by copyright.
Raftery said it was not necessary to do so in the extradition court.
Glazebrook: "You're saying ownership of copyright is irrelevant? But it can't be."
Raftery: "We don't have to have actual copyright infringement as part of the elements of the offence."
Instead, he said it was enough for the court to accept the US case the Megaupload accused were dealing in and discussing material which was categorised as protected in New Zealand.
Raftery said the case in the US court would be required to go further to show proof of copyright in the movies and music identified as part of the Megaupload case, and also who owned it.
He said there was also sufficient evidence showing the group knowingly conspired to violate copyright and enrich themselves through doing so.