Illinois requires a Firearm Owner's Identification (FOID) card to lawfully possess any firearm or ammunition in the state. The Concealed Carry License (CCL) is a separate, additional license required to carry a concealed firearm in public.
Both are issued by the Illinois State Police and are revocable for a range of triggering events: felony convictions, domestic battery convictions (federal Lautenberg Amendment), certain misdemeanor convictions, mental health adjudications, restraining orders, and pattern-of-conduct findings.
Revocation has cascading consequences. A revoked FOID requires surrender of all firearms in the holder's possession, can subject the holder to charges under the Aggravated Unlawful Use of a Weapon (AUUW) statute if a firearm is later possessed, and can permanently affect future eligibility.
Defense angles often involve restoration petitions filed with the Illinois State Police or the circuit court, depending on the basis for revocation. Underlying convictions in other states may not always trigger revocation if the conduct would not have been a disqualifier under Illinois law — which becomes a litigation point in some cases.