I think you’re wrong... It’s only legal if they prohibit all non-work discussions. So if they also block discussions about politics, sports, music, etc they can

I think you’re wrong... It’s only legal if they prohibit all non-work discussions. So if they also block discussions about politics, sports, music, etc they can block talk about unions. But they can’t target union talk specifically: Companies may prohibit workers from talking about nonwork issues in work areas during work hours. ... In other words, a company can prohibit extraneous conversation, but may not prohibit only union discussions while allowing employees to talk about anything else they wish. Source: https://www.nolo.com/legal-encyclopedia/shop-talk-rules-union-related-conversations-activities-work.html https://www.nolo.com/legal-encyclopedia/shop-talk-rules-unio...