Check out the article in the Free Press today on a recent Michigan Supreme Court decision. I see this more and more. If the plate is obscured by a trailer hitch or whatever, it is legal for police to stop you and investigate further plus write you a ticket. Same goes if your plate is so damaged it is unreadable. You have an obligation to take it back to the Secretary of State and trade it in for a new one.
Police can stop a vehicle if they can’t see license plate
The Michigan Supreme Court ruled that motorists must attach plates in a place where it can be seen without obstruction.
Check out this story on Freep.com: http://on.freep.com/1MBjKoZ