"Common sense sometimes matters in resolving legal disputes," says the court. Reversing a decision by the NLRB, the DC Circuit held that a telephone company can forbid employees to wear "Prisoner of AT$T" T-shirts when going into customer homes or were working in public. Southern New England Telephone v. NLRB (07/10/2015).
During contract negotiations in 2009 Communications Workers in Connecticut wore T-shirts with "Inmate # ____" on the front and "Prisoner of AT$T" on the back. The boss said they could not wear them if they were going into customer homes or were working in public. Many did anyhow, and 183 got suspended.
The NLRB generally allows employees to wear union insignia while working, and keeps employers from firing workers who do so. There's a "special circumstances" exception: A company may lawfully prohibit its employees from displaying messages on the job that the company reasonably believes may harm its relationship with its customers or its public image.
AT&T explained that it banned only employees who interact with customers or work in public from wearing the T-shirts. AT&T officials testified that the shirts could alarm or confuse customers, could cause customers to believe that AT&T employees were actually convicts, or could harm the company’s public image more generally.