Very few 401(k) cases have been tried or settled, but just the threat of litigation may change the terms surrounding company stock in 401(k) plans. Employees who own company stock in a 401(k) plan cannot individually join in shareholder class-action suits filed against their employer because they do not own shares directly. Instead, the shares are owned by the plan, which can join shareholder lawsuits. 401(k) participants can sue under certain provisions of ERISA laws, which oversee pension and other employee benefit plans.
See "Lawsuits put pressure on companies to change 401(k) plan rules 401(k) suits can lead to reforms", Kathleen Pender, San Francisco Chronicle, February 11, 2002