azurefly:
Legal rulings often depend upon the definition of words in the law (whether statute or common law). Those definitions are quite often not the same as common usage. For example, here in MA, in most of the statutes the word "firearm" means handgun, short-barreled rifle, or short-barreled shotgun. In otherwords, in most of the statutes in MA a full-length rifle or shotgun is not a considered a firearm. Consequently, you will repeatedly see the phrase "firearm, rifle or shotgun..." in MA law. Unless you carefully read the definition section of MA gun law, you would miss that fact and grossly misinterpret the law.
As layman, we tend to read the law and think we understand it. But we typically read it using the common usage definitions of the words in the statute. If the court uses a different definition (whether because the words are defined elsewhere in the statute or have been defined in precedent) we may be gravely mistaken.
In this issue, one question is where the statute reads: "are unloaded and enclosed in a case, firearm carrying box, shipping box, or other container" one important question is whether the courts consider a fanny pack to be a case. To you and I it is a case. But the law may consider otherwise. Legally it may be a case. Or it may not. Or it may be a gray area in IL law that has not been adequately settled. If the law considers that the pack is not a case, then he was violating the law.
I feel for those in IL. I grew up in the state and have family there. The clear intent of IL law is that it is illegal to carry a gun for defensive purposes. It is legal to transport a gun (e.g., between home and a shooting range, or home and a gun store, etc.). I'm not an attorney, let alone an IL attorney. To my uneducated eyes, it seems to me that he is, at best, right up against the legal boundary and could be on one side or the other, depending upon the interpretation of the court.
If you go around flaunting the fact that you are right up to a gray boundary of the law, don't be surprised if the authorities take a dim view. He was taking a very great risk. Note, I'm NOT saying the authorities behavior was correct. I'm saying that the authorities behavior was predictable.
Personally, I never want to be someone's test case, so I do my best to stay well away from the edges of the law.