"Our case will be that the police didn't properly consider Nicky Hager's right to protect his confidential sources. This is not just (hacker) Rawshark but dozens of other sources."
He said there was also an expectation in society that people had the right to pass on information as part of the freedom of expression. The warrant would impact on the freedom with which people would do so, he said.
The other strand of the case is a separate High Court case in which the police are seeking judicial advice over their rights of access to material seized during the search. Hager has claimed journalistic privilege over the material.
David Jones QC, who was speaking generally about the issue of journalists using unlawfully obtained material, said information sourced through a criminal act would be forever stained by the crime committed to obtain it.
He said "public interest" did not give open permission to society to invade privacy and commit crime so information taken could be disseminated.
"You could say there is a public interest in people knowing lots of things. Is there not a greater public interest in upholding the rule of law?
"The ends do not justify the means. That's really what it comes down to."
University of Canterbury law Professor Ursula Cheer said the "public good" of the Dirty Politics disclosures would likely be argued in court to show the use of the material justified protecting the source.
She said the potential chilling effect of revealing the source's identity might mean the public interest would not be served in future.
"We've never really had a case like this before and we've never really had any of these issues tested."
She said the closest was the case which stemmed from an interview between TV3's John Campbell and one of the men who stole medals from the Waiouru War Memorial Museum.
In that case, she said the judge pushed the police to fined a way of resolving the issue without compelling the media to disclose the source. When it emerged the police could not, the judge then created space in which TV3 and the police could resolve the matter without a formal court order.
"This case is different. There is a far greater public interest to be argued here."
The police investigation was launched after a complaint from blogger Cameron Slater, whose hacked email and social media conversations formed the backbone of Dirty Politics.
