This is about forest plan litigation – sort of. The Michigan Wilderness Act included a provision protecting “valid existing rights.” A series of forest plan amendments by the Ottawa National Forest imposed restrictions on motor boat use on a lake that was mostly within a wilderness area but partly touching private land. A 2007 Forest Order, subjected violators of Amendment No. 5 to criminal liability. An earlier case concluded that Michigan riparian water rights allowed for “reasonable use” of the lake’s surface water, and that, “the motorboat restrictions interfered with Thrall’s ‘valid existing right’ to use gas motor boats on Crooked Lake’ and thus fell outside the Forest Service’s regulatory authority.”
The question in the current case was whether purchasers of lakefront property in 2010 also had “valid existing rights” to unrestricted motorboat use. After sorting out the timing questions in favor of the private owners in this case, the Sixth Circuit court revisited the nature of riparian rights, holding that the Forest Service could only prohibit unreasonable uses:
“But the Forest Service has not shown that it would be unreasonable under Michigan law to travel on 95% of the lake above a low-wake-zone speed. If you think otherwise, try being at one end of a three-mile lake with a five-mile-an-hour speed limit as an unexpected storm sets in.”
(Evidently what’s reasonable in Michigan is different from what’s reasonable in wilderness.)