And what is the statue/law/public act/rule that requires that? I have lived here my entire life except my stint with the military and have not nor do I know of any such requirement. Possibly you are refering to a city/county ordinance?
If you don't have one of these you'll be in big trouble if they catch you.
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What is a FOID card?
The FOID card was created in 1968, by the FOID Act, as a way to identify those persons eligible to possess and acquire firearms and firearm ammunition as part of a public safety initiative in the State of Illinois.
Who needs a FOID card?
Unless specifically exempted by statute,
any Illinois resident who acquires or possesses firearm or firearm ammunition within the State must have in their possession a valid Firearm Owner's Identification (FOID) card issued in his or her name.
How do I transport a firearm through an Illinois community with an ordinance that prohibits firearms or handguns?
Illinois' Unlawful Use of Weapons law does not preempt local ordinances from banning firearms. Persons carrying or transporting firearms through such communities could be subject to local firearm ordinances. It is recommended that you contact local authorities regarding their firearm ordinances.