The Chief High Court judge has ordered the return of some of internet entrepreneur Kim Dotcom's property.
The material was seized from Mr Dotcom's house in Coatesville, near Auckland, in January last year during a police raid that has since been ruled illegal.
Kim Dotcom is fighting extradition to the United States on copyright, money laundering and fraud charges.
In a judgement released on Friday, Justice Helen Winkelmann said police must sort through the seized property and return any items not relevant to the case.
Justice Winkelmann also asked police to notify US authorities of her decision.
Mr Dotcom, a German national with New Zealand residency, had earlier asked the High Court for access to the material, saying the information would help him prepare for the hearing.
In June last year, the High Court ruled that the warrants used in the police raid were too broad, didn't describe the offences properly and were therefore unlawful.
Police said on Friday they are considering the judgement, but pointed out the ruling also requires Mr Dotcom to provide them with any passwords needed to gain access to laptops and hard drives to decide what is relevant.
A spokesperson said police would work with Crown Law to decide their next steps.
University of Otago law professor Kevin Dawkins said it will be an enormous undertaking for police. He told Radio New Zealand's Checkpoint programme the key issue will be what is deemed relevant.
"Her Honour makes a distinction between relevant and irrelevant material, and the relevant material is that which is related to the offences to which the warrant should have been limited."