Missouri Revised Statutes Title XXXVIII. Crimes and Punishment; Peace Officers and Public Defenders § 578.427. Labor union activities and other employee activities, exempt--local governments may adopt laws consistent with and alternative to

1. Sections 578.421 to 578.437 shall not apply to employees engaged in concerted activities for their mutual aid and protection, or the activities of labor organizations or their members or agents.

2. Nothing in sections 578.421 to 578.437 shall prevent a local governing body from adopting and enforcing laws consistent with sections 578.421 to 578.437 relating to gangs and gang violence. Where those local laws duplicate or supplement the provisions of sections 578.421 to 578.437, sections 578.421 to 578.437 shall be construed as providing alternative remedies and not as preempting the field.