I've been trying for a couple of months to get a straight answer from the Forest Service as to whether it's legal to land on National Forest Lands (outside Wilderness, of course). Everybody I've spoken to has said they're pretty sure it's illegal, but when I ask them to cite a regulation, they all tell me they'll get back to me.
That's the Custer/Gallatin NF and the DC Office.
For other land management agencies, it's fairly straightforward: NPS says not no, but hell no, and there's a regulation that applies to all National Parks in the Lower 48. Same for Fish and Wildlife Service Refuges.
For National Forest lands and BLM, not so clear. I'm pretty sure they'd all tell you no....but I'm looking for something in writing.
I suspect that so few people have landed airplanes off airport in the Lower 48 till recently, it's just not been an issue. That's rapidly changing, however.
MTV