"The secrecy surrounding the negotiations is, in my view unprecedented," Professor Kelsey said.
"Especially given the parties signed a pact right at the beginning that they wouldn't release any documents during the negotiations, and they keep all but the text secret for another four years beyond that. The stakes are too high here to allow that to go unchallenged."
While they would have preferred to have brought the case earlier, Professor Kelsey said, it remained crucially important to secure release of information before any deal was done and dusted, and to clarify the rules for future negotiations.
The case would go ahead no matter what happens in Hawaii this weekend, she said, where negotiations on the 12-country Pacific trade pact could wrap up.
"It's very disappointing it took the Ombudsman's office so long, because ideally we would have liked to have had it before the Ministerial meeting that will supposedly bring to an end.
"But there are many other processes where getting that information is important. Not only the debate that happens about the conclusion of the agreement, but there is also a process that the US will adopt called certification, which is where the US puts a lot of pressure on our Government to change what we've done domestically to comply with the agreement. And that needs to be out in the open. And in the current disposition of the Minister, that would take place in secrecy."
The challenge is important not just for the TPPA, but any future agreements were negotiations are veiled, Professor Kelsey said.