Constitution of the State of Illinois Art. I, § 25. Workers’ Rights

(a) Employees shall have the fundamental right to organize and to bargain collectively through representatives of their own choosing for the purpose of negotiating wages, hours, and working conditions, and to protect their economic welfare and safety at work. No law shall be passed that interferes with, negates, or diminishes the right of employees to organize and bargain collectively over their wages, hours, and other terms and conditions of employment and work place safety, including any law or ordinance that prohibits the execution or application of agreements between employers and labor organizations that represent employees requiring membership in an organization as a condition of employment.

(b) The provisions of this Section are controlling over those of Section 6 of Article VII.