DNR has permits for firewood on stateland. $25 for 5 cords, and if i recall it states full cords. they will have a map of where firewood cutting is open, mostly in recently cleared areas. i have found a lot of good firewood in those areas around me. i look along the edges of the clearcuts. trees along the edges get damaged, pushed down and break. if ya havent done it before, theres 2 things i would advise. 1) have an ORV permit. found out its needed to drive back in on any state land in any vehicle. 2) go scope out the areas that are open before loading up and heading out to cut. some of the areas are pine stands and nothing for hardwood worth workin for.
as for federal land, i dont believe cutting firewood is permitted.