Slater's legal action specifically targeted the New Zealand Herald, TV3 and Fairfax Media, as well as the "unknown" hacker behind the Whaledump Twitter account.
His lawyer John Billington QC said his client suspected he knew the identity of Rawshark but was not sure enough to name him.
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The case, which the lawyer suggested was a first in the country's legal history, was likely to shape the way the law was used in the future.
He compared the scenario to a thief breaking into someone's bedroom and stealing personal information which then ended up on the front page of the paper.
The lawyer acknowledged Justice John Fogarty must balance the public interest against the right to privacy but said "the court can't close its eyes to the fact the information was obtained by crimes".
"It's also in the public interest upholding law and order," Mr Billington said.
Julian Miles QC, representing the media outlets, said the application for an injunction had come far too late and he called the situation "unprecedented in New Zealand political history".
He criticised Slater's affidavit, which he said focused on personal information the media had no interest in publishing.
"The continuing pattern of what's been published is significant issues of genuine public interest which all relate to the political debate that's raging at the moment," Mr Miles said.
There were also references to TV3 director of news Mark Jennings' affidavit in which he made scathing comments on Slater's previous personal attacks on people that had caused "immense distress and damage".
Mr Miles said a ban on publication even for one day would be hugely significant so close to an election.
"It would be irresponsible to gag informed commentators but the Wild West, as it were, in the blogosphere would be free to disseminate conspiracy theories and allegations and whatever else they might want."
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Whether or not an injunction was granted, he said information would continue to come out through various sources online and it was best to allow the mainstream media to disseminate it responsibly.
Just before this afternoon's hearing, Rawshark announced he would stop releasing the hacked communications under the Whaledump account but also threatened a return if dirty politics continued in New Zealand.
"I know vigilantism is a dangerous final resort. I hope history judges me kindly," he said. "If I didn't do it, who would have? If I didn't do it this way, how could it have been done?"
Mr Slater's statement of claim said he had "tens of thousands of emails spanning a period of more than ten years", including exchanges with accountants, doctors, lawyers, psychiatrists and personal communication with his wife.
The High Court showdown comes two weeks after the publication of Nicky Hager's Dirty Politics book, which accused the National Party of attacking opponents through Slater's Whale Oil blog.
