An inquiry into the police investigation found substantial flaws which were said to have not had a serious impact on its outcome.
The latest stage in his campaign was an appeal to the Governor-General for mercy - which led Power to order a new inquiry by senior lawyer Kristy McDonald.
The details of the inquiry are secret until revealed by Power, who is about to leave politics for a senior banking job.
"I believe it should go back to the Court of Appeal," said Hide. "This is why we have Parliament and ministers because they do have the ability to over-ride the system when it gets off track. That is what has happened here."
The Herald on Sunday understood McDonald's report placed emphasis on an assumed requirement there be "new evidence" to trigger a referral back to court for Watson - or a pardon.
It is understood the report said there was no new evidence and so the plea for clemency must fail.
However, Hide said any inquiry must go further.
"What's concerned me is the call for new evidence when it was the existing evidence which clears Watson."