820 ILCS 90/15: Enforceability of a covenant not to compete or a covenant not to solicit.

A covenant not to compete or a covenant not to solicit is illegal and void unless (1) the employee receives adequate consideration, (2) the covenant is ancillary to a valid employment relationship, (3) the covenant is no greater than is required for the protection of a legitimate business interest of the employer, (4) the covenant does not impose undue hardship on the employee, and (5) the covenant is not injurious to the public.