The Crown is appealing a High Court ruling that search warrants used in the Kim Dotcom case were illegal.
Chief High Court Justice Helen Winkelmann's ruled last month that search warrants used to raid Dotcom's Auckland mansion were invalid.
Dotcom, 37, ran the world's largest file-sharing site from his $30 million mansion in Auckland, before he was arrested in a dramatic raid on charges of money laundering, racketeering and copyright infringement.
Justice Winkelmann said the search warrants were invalid because they were general warrants which lacked specificity about the offence and the scope of the items to be searched for.
Without a valid warrant, police were trespassing and exceeded what they were lawfully authorised to do.
Justice Winkelmann said no one had addressed whether police conduct also amounted to unreasonable search and seizure, but her preliminary view was that it did.
Dotcom, 38, is on bail awaiting an extradition hearing.
United States authorities say he and his three co-accused - Mathias Ortmann, Fin Batato and Bram van der Kolk - used Megaupload and its affiliated sites to knowingly make money from pirated movies and games.
Dotcom is charged with multiple copyright offences.
- © Fairfax NZ News
Family counts blessings after superbug scare (graphic content)
Have you moved cities recently?Related story: Kiwis like to shift cities - survey
The power of googoo eyes (pictures)
Google Now is the future
New season shows to look forward to
The vanilla Budget
A day of building in time-lapse video
So-called sweets I'll never eat again
A fascinated fear of bugs
Nintendo, whata you up to?
Messing with their heads
Daft Punk's brand new album
Navigating life as an intersex character
Wedding woe: Upgrading the ring