Thankfully Michigan has a muzzle loader season after the regular fire arm season. If it is above 45cal scoped or not scoped it is legal.
We in Michigan also know they were building in line muzzle loading rifles as early as 1836. I often wonder where the primitive folks stop at a weapon being primitive.
I would say any thing past the split stick with a nice rock woven into the split is primitive and arrows with real flint heads. Other wise they aren't really very primitive.
Scoped or not should be up to the hunter if legal in their state. I can't even fathom why any one would want to fight the scope non scope question, as it should just be up to the hunter just as it is the modern rifle.
Al