A ruling that search warrants used in a police raid on Kim Dotcom's mansion were unlawful is a "significant blow" to the police and the FBI, the internet tycoon's lawyer says.
The German national was arrested after police swooped on his home in January and stands accused of breaching copyright laws costing owners more than US$500 million. US authorities are attempting to extradite him to face the charges.
Justice Helen Winkelmann found the warrants did not adequately describe the offences to which they related.
"Indeed they fell well short of that. They were general warrants, and as such, are invalid."
US lawyer Ira Rothken told TV ONE's Close Up after reading the search warrant, the court was left with the "logical conclusion" that it was "over-broad" and invalid.
"[The warrants] dealt with anything related to some generic offence of copyright, and that would not only include hard drive data, but almost anything in the house - from DVDs, family photos, to a newspaper.
"With so little guidance, the police pretty much confiscated all digital media, regardless of the privacy implications, and regardless of whether it's related to the case at all."
Rothken said he was confident in his client's case because the merits seemed to be on Dotcom's side.
"These types of findings will certainly have consequences on the Government's case.
"Especially for, what the US is calling, the biggest copyright case in history."
Winkelmann also ruled it was unlawful for copies of Dotcom's computer data to be taken out of the country, and any cloned items or copies are not permitted to leave New Zealand.
She instructed the Attorney-General to return any clones or copies of the hard drives held by New Zealand police.
An independent lawyer will now review the seized items and determine which are relevant to the investigation. Relevent items will be provided to US authorities and the rest will be returned to Dotcom.
Dotcom told ONE News last night he still could not be believe what happened to him.
"This Osama Bin Laden style raid on my house and, you know, locking me up, seizing all my assets."
A spokesman for Dotcom said tonight the alleged internet pirate was "pleased", but he would not be making any further comment on the decision as appeals were likely.