Organizing Rights Under the Railway Labor Act

Under the RLA, an employer is prevented from:

Surveillance of organizing activities
Threatening to sue in an effort to suppress support
Terminating/disciplining or threatening to terminate/discipline employees for supporting the union
Barring employees from soliciting cards or membership during non-work time and in non-work areas as long as the Company does not have a specific and non-discriminatory policy banning all solicitation (a non-work area generally includes break rooms, crew lounges, anywhere where work is not performed)
Asking about confidential union matters (i.e. whether or not the employee signed a card)
Asking about whether the employee supports the union
Threatening to discontinue existing benefits
Promising to give employees promotions, raises, or other benefits in exchange for voting against the union
Endorsing one Union over another
Preventing an employee from voting
Knowing how the employee voted
Prohibiting an employee to wear his pin on the job as long as it does not contain a controversial statement or violate company policy or uniform requirements
Preventing an employee from handing out leaflets on his own time in non-work areas
Preventing an employee from discussing the prospect of a union while at work as long as it does not interfere with work duties (contrast this with how an employee should only hand out representation cards during non-work time in non-work areas)

45 U.S.C. § 152 (Third), (Fourth); 29 C.F.R. § 1205.2