Employees' rights of expressive association and freedom of speech in forming association for mutual aid and support is protected under the First Amendment whether or not state law will permit the association to become an exclusive bargaining agent for the employees. Denial of qualified immunity upheld, as this was clearly established at the time.
http://www.ca5.uscourts.gov/opinions/pub/17/17-40754-CV1.pdf
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.