Williamson v. Cox Communications, Inc.

At Home Corporation, a high-speed internet company, was founded by TCI, with Cox (defendant) and Comcast (defendant) holding minority stakes. Each of the three could appoint a director; a distribution agreement made the cable companies use and fund At Home; and, after AT&T acquired TCI and could not meet its customer commitments, the certificate was amended to require four of five Series B directors to approve board action, giving Cox and Comcast veto power. AT&T later pushed through transactions that benefited AT&T, Cox, and Comcast at At Home's expense, after which At Home went bankrupt. At Home's bondholders (plaintiffs) sued Cox and Comcast for breaching controlling-shareholder fiduciary duties; the defendants moved to dismiss, denying they controlled the company.

Whether a stockholder is a controlling shareholder - owing fiduciary duties - when it either owns more than half the voting power or actually exercises control over the corporation.