Hi Alex, yes sir, since this does not have a threaded barrel, it is legal in Illinois. The compensator makes use of Shadow’s patent-pending attachment method which eliminates space wasting threads. An internal locking lever rigidly mounts the comp to the proprietary tri lug barrel.
Stay safe & have a great day!

Yes it is legal in Illinois budsgunshop.com/feeds/state_reg/illinois_restrictions.pdf

Hi Alex and welcome. Yes Sir, 100% IL legal as configured. Cheers, stay safe and enjoy!

Legal in Illinois
budsgunshop.com/feeds/state_reg/illinois_restrictions.pdf

Yes, this is good to go in Illinois as...
A compensated pistol is generally legal in Illinois. However, there are some restrictions. Specifically, muzzle brakes or compensators are not explicitly prohibited in Illinois, but they cannot be attached to an assault weapon as defined by the Protect Illinois Communities Act. Additionally, any device that increases the rate of fire of a firearm, like a bump stock, is prohibited.