Right To Organize
Organizations through unionism is a legal right.
This has been in effect for over 65 years guaranteeing workers freedom of organization.  Here is what the law says (Quatation from the “National Labor Relations Act”)

”Employees shall have the right to self-organization to form, join, or assist labor organizations ..”

”It shall be an unfair labor practice for an employer-to interfer with, restrain, or coerce employees in the exercise of the rights guaranteed - (above)”