Illinois Supreme Court & Chicago Assault Weapons Ban

The Illinois Supreme Court in Wilson v. Cook County (2012) has held that whether the banned assault weapons are protected by the Second Amendment is a matter of fact to be re-examined by the trial court:

Plaintiffs seek to present evidence to support their allegation that this particular Ordinance encompasses a myriad of weapons that are typically possessed by law-abiding citizens for lawful purposes and fall outside the scope of the dangers sought to be protected under the Ordinance. Without a national uniform definition of assault weapons from which to judge these weapons, it cannot be ascertained at this stage of the proceedings whether these arms with these particular attributes as defined in this Ordinance are well suited for self-defense or sport or would be outweighed completely by the collateral damage resulting from their use, making them “dangerous and unusual” as articulated  in  Heller.  This  question  requires  us  to  engage  in  an empirical inquiry beyond the scope of the record  and  beyond the scope of judicial  notice  about the  nature of the weapons that  are banned  under  this  Ordinance  and  the  dangers  of  these  particular weapons.

This is not an ideal result, but the question of whether assault weapons are commonly owned for lawful purposes by civilians is going to end up with the answer: "Yes."  To justify a ban in spite of this will require Chicago to demonstrate that such weapons are dramatically more dangerous than other firearms.  That they won't be able to do.