Illinois does not have any ban on "assault weapons". There are some local exceptions.
Cook Co. Code of Ord. §54-211, Chi. Mun. Code §8-20-170
What is Assault Weapon Restrictions?
Some states have restrictions, banns, or require owners to register firearms they conceder to be "assault weapons". The definitions of an "assault weapon" varies widely from state to state. These definitions can include whether the gun is fully automatic, the magazine size it can carry, and others.