The High Court has ruled that Leslie Buckley is entitled to claim privilege over all but one of 11 documents disclosed as part of an investigation by the Office of the Director of Corporate Enforcement.
Mr Buckley is due to step down shortly as chairman of Independent News and Media.
The ruling by the High Court President, Mr Justice Peter Kelly, means Mr Buckley does not have to reveal the documents to the ODCE.
The Director of Corporate Enforcement is investigating a whistleblower complaint made by INM's former Chief Executive Robert Pitt against Mr Buckley arising from an aborted bid for Newstalk.
It had sought a range of documents from Mr Buckley.
Mr Justice Kelly read the 11 documents and said this morning, that all but one of them, was privileged, and should be returned to Mr Buckley without being seen by the director.
Mr Buckley represents INM's main shareholder, Denis O'Brien.
The ODCE's inquiry has been widened to take in the handling of a "potential personal data breach" at INM.
The only document found by Mr Justice Kelly not to be privileged was a letter from the ODCE itself, which was attached to an email.