When it comes to enforcing your organization's dress code, consistency is the name of the game.
As the following case shows, you can't prevent employees from wearing union-related shirts, hats and buttons if you allow them to wear similar nonunion items. You can, however, institute a nondiscriminatory dress code that prohibits certain types of both union and nonunion clothing or paraphernalia, such as a "no-hats" rule, or requiring employees to wear a uniform.
Recent case: The dress code at Quantum Electric, an electrical contracting firm, said employees' clothing or hats weren't allowed to contain graphics or printed text other than that of the company name or logo. But, in reality, the company routinely let employees wear clothing with a host of other logos, such as "Marlboro," "UCLA" and "Harley-Davidson."
When employee Damir Tomas came to work wearing a T-shirt with an International Brotherhood of Electrical Workers Union logo on it,told him to turn it inside out. The employee refused and was told if he continued, he'd be written up and discharged. When Tomas again refused to hide to logo, he was fired.
He sued, alleging the company violated the National Labor Relations Act (NLRA).
The National Labor Relations Board (NLRB) agreed, saying the company couldn't show that its ban on wearing the union-related shirt was necessary to maintain employee production or discipline or to ensure safety. So the company's decision to discharge him violated the NLRA. (NLRB v. Quantum Electric Inc., 341 NLRB No. 146, 2004)
Final note: This ruling shows another example of why nonunion organizations need to be aware of the requirements of the main union-related law, the NLRA.