Knife laws are not preempted. Any knife could possibly be unlawful to carry in certain communities and venues. And if a person is carrying a gun at the same time, severe problems may arise.
THIS^^
Better to leave it at home when OCing. Why? Makes it really easy on shady PD's to hassle a otherwise legal OCer. If you really want to carry a knife, work with others to get knife preemption laws passed in MI. There's a reason most cities and villages have knife laws on the books, just as they still have outdated gun laws on their books. It is just one more thing a "bonus" local charge/violation to be hurled at someone who they don't like. Many local PD's don't like OCers, so you do the math.
My mind goes back to a member Fatman/Chuckwagon, who carried a pocket knife while OCing. He got jammed up in Southgate MI, while at a restaurant with his family. One of the local OEO's (opinion enforcement officers) took issue with his OC. Not being able to do anything about it legally, the officer noted a "suspicious bulge" in his front pocket & searched him for "officer safety". Turned out to be a very small pocket knife, that which many MI men carry daily. No matter, this was enough for the officer to arrest him, and take him to jail for a short while until bail could be posted. Bogus? Yes. Technically legal? Yes. The judge tossed the concealed weapon charge on the basis that the search was based on the legal activity of OCing, therefore, fruit of the poisonous tree.
My point - is carrying a $10 - ?? Dollar knife worth the thousands of dollars it could take to defend against "technically legal" charges brought by a "OEO"?
In the end Fatman sued them, and won a small settlement. Was it worth the hassle and time lost from work and family? Only he can answer that.
As always YMMV, you maybe a lawyer, with infinite time on your hands to file legal actions.