sorry it not Illinois legal. taurus makes one that may fit your need it is out of stock now but should be back in stock soon budsgunshop.com/product_info.php/products_id/113303/taurus+1tx2234110+tx22+.22+lr+4.10+10+1+black+anodized+aluminum+slide+ergonomic+black+polymer+grip

Hi Kevin, your FFL is correct. A semi-auto pistol cannot have a threaded barrel in Illinois. Unfortunately S&W does not make this with a non-threaded barrel.
The only legal path to ownership for this gun would be to buy it locally and have the thread protector pinned/welded.
Stay safe & have a great day!

No, not unless you were law enforcement. They are exempt from restrictions us civilians have to adhere by.

Hi Kevin and welcome. Unfortunately, not as long as it is Semi-Auto with a detachable magazine and threaded barrel. A handgun must comply with PICA regulations. A handgun is regulated by PICA if it has any features set forth in 720 ILCS 5/24-1.9(c)(e.g. a threaded barrel). Cheers and stay safe!