There are certain forest roads that require permits. Riverbeds are a gray area that's not legal and not really illegal. They make effort to close many of them, but dirt bikes and 4x4s always find a way in and I've never heard of anyone ticketed. In the south there are a couple where the local tribes are really against people being there and they'll let you know that you need to go back. One they closed to 4x4s so you need to hire their Delicas if you want to access the hot springs. Clearly a money grab.