I personally don’t know, but if someone else here doesn’t, you could always check with the Michigan Geocaching Organization (http://www.mi-geocaching.org/) since that area is in Michigan.
I was just browsing the cache map, and see there are some in the Ottawa National Forest:
Burned Out – http://www.geocaching.com/seek/cache_details.aspx?ID=88297
Nature’s Gas – http://www.geocaching.com/seek/cache_details.aspx?ID=88281
You could look at either of those, then click on “find nearby caches” to find more.
But as for whether they are allowed…. That’s out of my realm of knowledge….
Such a beautiful area there – maybe I’ll just end up finding some of your caches there this summer! 😉