The court's ruling in Nicky Hager's favour greatly affects the general public because of the vital role journalists play in sustaining a functioning democracy, a media law expert says.

The High Court today ruled police unlawfully searched Hager's house in the hunt for identity of the hacker who supplied information for the Dirty Politics book.

Media law expert Professor Ursula Cheer explained why the ruling was not only important for journalists, but the public too.

•Chilling details of intrusion into Nicky Hager's privacy

•Police house raid on investigative journalist Nicky Hager found to be unlawful


"For citizens to be able to understand what is going on, who is governing them and who is spending money on their behalf and whether people are behaving according to the rule of law and all that, then journalists need to be out there holding power to account," Ms Cheer said.

"Often they have to get information from people who don't want their identity to be made public and those people probably wouldn't give their information if they thought their identity would be made public, so that is what confidentiality of sources is all about. Join the dots and journalists are doing a job on our behalf because we don't have time to investigate and find out what is going on."

Ms Cheer said it set a precedent about was acceptable and unacceptable police behaviour around seeking warrants to raid journalists' homes.

"This really affirms to police what the Court of Appeal said about 10 years ago before this new Search and Surveillance Act applies if they are going to get warrants against journalists," she said.

"It all ties back to journalists actually doing a really useful job which is holding power to account. They need to have their sources and their sources need to know they can trust the journalist so the law needs to be very very careful before it allows something to happen that might damage those relationships.

"It is not just a rarefied decision that makes journalists happy, it [allows] journalists to get on and do the job that they are doing on our behalf."