Shari Redstone and her family’s National Amusements Inc. holding company cannot access privileged communications between a special committee of CBS directors and the company’s Wachtell, Lipton, Rosen & Katz attorneys—in an ongoing dispute over control of the New York-based media giant, a Delaware Court of Chancery judge ruled on Friday.

The ruling, from Chancellor Andre G. Bouchard, followed weeks of jockeying over corporate records as CBS and its controlling shareholder prepare for a high-stakes trial scheduled to begin in October.

Shari Redstone. Photo: David Paul Morris/Bloomberg