In his ruling, Appeal Court Justice Stephen Goudge said he was persuaded that only a handful of the documents should be kept from the inquiry because they enjoy solicitor-client privilege.
At issue were about 350 emails and other materials — whittled down from about 600 — that mall owner Bob Nazarian and family members refused to hand over to the commission.
The Nazarians argued the letters and emails were privileged and should remain confidential but commission lawyers argued there was no evidence to support that claim.
Goudge made it clear he found some of the reasons put forward by the owners for their position baffling.
"I cannot conclude that this cryptic explanation warrants a finding that these communications are subject to solicitor-client privilege," Goudge wrote about one group of contested documents.
"I would dismiss the claim for privilege because there is no showing that the communication forwarded was for the purpose of legal advice, a fundamental precondition for privilege," he said of another group.
Goudge, who arbitrated the issue, did find about a dozen documents were entitled to secrecy.
The public inquiry has been fighting over document access with the Nazarians since last fall. At one point, the matter was headed for Divisional Court until the family relented in March and turned over about 85,000 emails.
The Nazarians later claimed blanket solicitor-client or litigation privilege over 1,950 of those emails but the numbers shrank substantially.
In their application to Goudge, the commission argued the emails involved third parties and were not subject to secrecy rules.
Nazarian owned the Algo Centre Mall in Elliot Lake, Ont., when it collapsed June 23, 2012, killing two women and injuring several others.
Witnesses at the public inquiry have said Nazarian pressed them to minimize evidence of the mall's crumbling infrastructure, refused to make necessary repairs, and bullied or badgered employees and contractors who raised concerns.
Nazarian and his son Levon are scheduled to testify before the inquiry this month.