From the FAQ at Michigan Open Carry,
15. I don't live in Michigan. Can i open carry in Michigan?, scroll to the bottom of post for their opinion...
15. I don't live in Michigan. Can I open carry in Michigan?
It depends. MCL 28.422 states:
(1) Except as otherwise provided in this act, a person shall not purchase, carry, possess, or transport a pistol in this state without first having obtained a license for the pistol as prescribed in this section.
There is a relevant exception to this listed in subsection (8):
(8) An individual who is not a resident of this state is not required to obtain a license under this section if all of the following conditions apply:
(a) The individual is licensed in his or her state of residence to purchase, carry, or transport a pistol.
(b) The individual is in possession of the license described in subdivision (a).
(c) The individual is the owner of the pistol he or she possesses, carries, or transports.
(d) The individual possesses the pistol for a lawful purpose as that term is defined in section 231a of the Michigan penal code, 1931 PA 328, MCL 750.231a. (Editor's note: MCL 750.231a was modified by PA 427 of 2012 which removed this definition so this language is a left-over that needs to be cleaned up by the legislature)
(e) The individual is in this state for a period of 180 days or less and does not intend to establish residency in this state.
The law also prescribes a penalty for non-compliance:
(9) An individual who is a nonresident of this state shall present the license described in subsection (8)(a) upon the demand of a police officer. An individual who violates this subsection is guilty of a misdemeanor punishable by imprisonment for not more than 90 days or a fine of not more than $100.00, or both.
So, to answer the question, do you have a license from "your state of residence" to "purchase, carry, or transport a pistol"? It is our belief, for the purposes of MCL 28.422 an Illinois FOID (Firearm Owner ID) card would meet this requirement, provided the person "resides" in IL. We also believe that a Concealed Pistol License (CPL), Concealed Weapons License, or equivalent that was issued by your state of residence would also qualify you for this exemption.