If an establishment has a liquor license, whether they sell/serve alcohol or not, it is illegal for a person to possess a firearm on the "premises".
"Possess" means to have it and "premises" means the entire property. And that means it is illegal for a person who does not have a CPL to have a gun, even locked in the trunk of his/her car, anywhere on that property ... including the parking lot.
http://www.legislature.mi.gov/(S(vsxqzy45fmo05c45s5byp145))/mileg.aspx?page=GetObject&objectname=mcl-750-234d
THE MICHIGAN PENAL CODE (EXCERPT)
Act 328 of 1931
750.234d Possession of firearm on certain premises prohibited; applicability; violation as misdemeanor; penalty.
Sec. 234d.
(1) Except as provided in subsection (2), a person
shall not possess a firearm on the premises of any of the following:
-snip-
(h) An establishment licensed under the Michigan liquor control act, Act No. 8 of the Public Acts of the Extra Session of 1933, being sections 436.1 to 436.58 of the Michigan Compiled Laws.
(2) This section does not apply to any of the following:
-snip-
(c) A person licensed by this state or another state to carry a concealed weapon.
-snip-
Now a word of caution for OC'ing without a CPL...
When transitioning from "transporting" to "carrying" be very careful to do ALL handling of the gun itself OUTSIDE the confines of the vehicle. DO NOT handle the gun inside the trunk trying to hide what you are doing from folks in fear of scaring them. Also .. do not lean back into the vehicle to get a hat or anything and have the gun now on your hip go inside the car.... because unless transporting..... without a CPL it is illegal to possess a pistol inside a vehicle....
http://www.legislature.mi.gov/(S(oxd4ik45z1v2x4arawzlnjin))/mileg.aspx?page=GetObject&objectname=mcl-750-227
THE MICHIGAN PENAL CODE (EXCERPT)
Act 328 of 1931
750.227 Concealed weapons; carrying; penalty.
Sec. 227.
-snip-
(2) A person shall not carry a pistol concealed on or about his or her person, or, whether concealed or otherwise, in a vehicle operated or occupied by the person, except in his or her dwelling house, place of business, or on other land possessed by the person, without a license to carry the pistol as provided by law and if licensed, shall not carry the pistol in a place or manner inconsistent with any restrictions upon such license.
-snip-
So, without a CPL, the only legal way to transition from "transporting" to "carrying" is to take the gun completely out of the vehicle still in the case and then handle it.
And be sure to reverse the process when transitioning from "carry" to "transport".