Isn't there something in IL law that allows local government to be more lenient, but not stricter. (as concerns firearms).
Just from researching this - I think the opposite is true. Municipalities can pass more stringent regulations on firearms, but the Illinois UUW law - is just that - it's a law, a state law.
There is the Hale Demar law which prohibits municipalities from prosecuting someone for firearms violations when they are defending themselves. The Hale Demar law provides "that it is an affirmative defense to a violation of a municipal ordinance that prohibits, regulates, or restricts the private ownership of firearms if the individual who is charged with the violation used the firearm in an act of self-defense or defense of another"
But that's actually a state law that protects people from punative local laws... not exactly the same thing as what you're making reference to.
I don't see anything that gives counties or local authorities discretion on enforcing state law for UUW.