As a Michigan resident I'm telling you the Michigan preemption does not include colleges. They have the power to create ordinaces to ban firearms on campus. If you were to get caught you could maybe make some argument that the community college can't ban firearms and must follow state law but you will probably lose. If you want to be 100% legal leave your gun at home or park off campus.
And LEO can carry nation wide, citizens can't. Unfortunately LEO and regular citizens aren't the same as far as where they can and can't carry.
EDIT: This a a post from "TheQ" from opencarry.org. He is not a lawyer, this is not legal advice this is just what many of us have found reguarding carry on campus in Michigan.
"In Michigan, Community College and Public Universities via their operating board have the power to pass ordinances -- much like any other local government (City, etc.) would. These ordinances are enforced the same was as they would be in a city. The University/College has a dedicated police force to their institution (often bearing said institution's name). These are sworn police officers that carry guns, handcuffs, often MiCOLES certified. These officers have arrest powers and can and will arrest anyone within their jurisdiction found to be violating the law (State Law of their local ordinances). People found to be in violation of the local ordinances are criminally taken (or civilly in the case of a civil infraction) to the local court and treated appropriately.
Now comes the question of MCL 123.1102, aka "preemption". MCL 123.1101 specifically spells out Cities, Townships, and Counties. It does not list community colleges and universities. Furthermore, unlike an "Authority" (See CADL) they weren't even brought into existence by a City, Township, or County. Universities have absolutely no legal affiliation with their host City, Township, or County. Therefore it could very easily be argued (and in front of Judge Aqualina of Ingham County) that Colleges/Universities do NOT fall under preemption. Therefore, the common wisdom (until we get preemption fixed) is that University ordinances ARE ENFORCEABLE and law abiding citizens should behave appropriately in this regard.
I hope this answers your question."
http://forum.opencarry.org/forums/showthread.php?94171-Michigan-State-University-OC