Q. "In light of some heated conversations, can we tell employees not to discuss politics at work?"
Answer:
Yes, you can limit political speech that is not work-related provided you don't infringe on protected Section 7 rights or applicable state laws. Section 7 of the National Relations Act gives non-supervisory employees the right to talk about the terms and conditions of their employment and unionize. While this law protects some political activities, it doesn't give employees the right to discuss politics during work unless they have an impact on the terms and conditions of their employment.
It might be best, though, to focus on the effects these discussions could have on job performance rather than the specific topic. If an employee spends too much time in casual conversation, regardless of the topic, they may not perform their best or could distract others. If volume and conduct during these conversations is a problem, remind employees of the standards for appropriate workplace behavior.