Illinois makes it illegal to own automatic weapons in the state. While in other states, you can own certain classes of automatic weapons, Illinois is not among the states that allow such a weapon within its borders. Further, you cannot take a handgun and then refurbish it to fire multiple rounds with a single trigger pull. Lastly, you cannot own a weapon if you have been convicted of certain felonies.
Now, one man is accused of breaking all three laws after selling a modified Glock to an informant. He has been charged with unlawful possession of a weapon by a convicted felon, modifying a Glock, and illegal possession of a weapon in the State of Illinois.
To be certain, a modified Glock capable of shooting multiple rounds with a single trigger depression is not legal anywhere in the United States, including Texas where automatic weapons can be owned and purchased so long as they meet specific criteria.