Lawyers for Kim Dotcom are seeking to get back items seized in the police raid on the billionaire's mansion, claiming parts of the search were unlawful.

During the initial search, authorised by Judge David McNaughton, police took dozens of items including anything that could store digital data, meaning home videos, CCTV footage and data from the mansion swimming pool heating system were seized.

Paul Davison QC, for Dotcom, and a lawyer for the Attorney General appeared briefly at the High Court in Auckland today where a date was set in May for the case to be discussed.

ACCUSED: Kim Dotcom.

It was agreed that none of the items seized would be sent to the US before the date set in court.

Before the appearance, Davison told media he believed some of the terms were unlawful and they would be seeking back many of the items seized.

Dotcom, 38, founded file-sharing site Megaupload and stands accused of breaching copyright laws costing owners more than US$500 million in what US authorities call the "mega conspiracy". They are attempting to extradite him to the US to face charges.

The internet tycoon was jailed after a raid on his $30m Coatesville mansion in January, and later won bail when the court deemed he was not a flight risk.

He is at the centre of the controversy surrounding Act leader John Banks, after claiming he gave Banks $50,000 in donations for his 2010 Auckland mayoralty campaign. Banks denies knowing Dotcom made the donations. Police are investigating whether Banks knew the sources of the donation, and that of a $15,000 donation from Sky City, both of which were declared anonymous.

Banks also updated the German billionaire on his application to buy property in New Zealand after receiving information from the office of Land Information Minister Maurice Williamson, the ACT leader's office says.

Dotcom applied to the Overseas Investment Office last year to buy the $30m mansion, a $5m neighbouring property and a $10m beach house at Northland's Doubtless Bay.