Kim Dotcom's lawyer says it will be utter nonsense if he can't question the reliability of evidence to be brought against his client at his extradition hearing.
Mr Dotcom, a German national who has residency in New Zealand, was arrested in January this year when 70 police raided his mansion near Auckland during an investigation into the Megaupload website he co-founded.
Mr Dotcom and three other men are facing extradition to the United States to face copyright, money laundering and fraud charges.
A judicial review began at the High Court in Auckland on Wednesday over an earlier court ruling allowing Mr Dotcom's defence team access to evidence within New Zealand.
Mr Dotcom's defence teams have earlier said that the evidence is vital for their preparation for his extradition hearing.
A lawyer for Mr Dotcom, Paul Davison, QC, says that without access to the evidence, he can't question its reliability and if the judge presumes that the evidence is accurate, it will essentially rubber-stamp his client's extradition.
John Pike, the lawyer for the Attorney-General, told the court on Wednesday the evidence is not important to the defence because Kim Dotcom is not standing trial in New Zealand.
Mr Pike said it is up to the judge in the extradition hearing to determine whether the evidence is sufficient to extradite the internet entrepreneur.
Lawyers for both sides say an extradition hearing scheduled for August is likely to be postponed.
The judicial review is expected to continue on Thursday.
Hearing on seized evidence delayed
A High Court hearing on what should be done with evidence illegally seized from internet millionaire Kim Dotcom's house has been delayed.
Last week, the Chief High Court Judge ruled warrants used in a police raid on Mr Dotcom's Auckland mansion in January were too broad and did not describe the offences properly, so were unlawful.
Justice Winkelmann was to discuss the impact of her ruling with Mr Dotcom's legal team and Crown lawyers acting on behalf of the FBI on Wednesday.
However, lawyers for the defence and the Attorney-General said they needed more time to prepare their arguments.
Hollywood involved, Dotcom claims
Kim Dotcom on Wednesday spoke out about what he claims is the involvement of the US government and Hollywood in his case.
Computer news website TorrentFreak is reporting Mr Dotcom as saying US Vice-President Joe Biden and senior Motion Picture Association of America staff as being behind the case.
Outside court, Mr Dotcom said everyone who has looked at his case has realised that the US government is trying to pioneer a whole new area of law, along with the power of Hollywood.
"Hollywood is one of the most significant contributors to the campaign of (Barack) Obama and his re-election. So when you look at all of this, I think this is really a commercial interest by the United States."