OK, I did the legal thing and asked the question on the MSP (Michigan State Police) website.
Got an email reply this morning. Here it is:
Thank you for posting your question to the MSP website. It has been forwarded to my office for a response.
question: When running wide aftermarket tires on a passenger vehicle, are there any laws governing how far a tire can protrude from a wheel well?
Sgt. Steven Spink
Michigan State Police
Traffic Services Section, Field Support Unit
East Lansing Headquarters
OK, now I have done a follow up question to him: How do I handle the situation when pulled over? Waiting for his reply.