765 ILCS 721/5: Prohibition on retaliatory conduct by landlord.

It is declared to be against public policy of the State for a landlord to take retaliatory action against a tenant. A landlord may not knowingly terminate a tenancy, increase rent, decrease services, bring or threaten to bring a lawsuit against a tenant for possession or refuse to renew a lease or tenancy because the tenant has in good faith done any of the following:

(1) complained of code violations applicable to the premises to the relevant governmental agency, elected representative, or public official charged with responsibility for enforcement of a building, housing, health, or similar code;

(2) complained of a building, housing, health, or similar code violation or an illegal landlord practice to a community organization;

(3) sought the assistance of a community organization to remedy a code violation or illegal landlord practice;

(4) complained or requested the landlord to make repairs to the premises as required by a building code, health ordinance, other regulation, or the residential rental agreement;

(5) organized or become a member of a tenants' union or similar organization;

(6) testified in any court or administrative proceeding concerning the condition of the premises; or

(7) exercised any right or remedy provided by law.