Like what has already been said, it is ultimately up to the local ranger district. Now from my personal knowledge, the gates are closed to keep vehicles out of that area until its reopened for the summer or in some cases closed permanently. Whatever the case, unless it is an archeological site or protected plant area....which should be identified, it is open to prospecting in accordance to surface management and state regulations.
Additionally if you're not familiar with it already, anytime you'll be on USFS land stop at a ranger district office and pick up a motor vehicle use map. The travel management plans have been implemented and not all roads are clearly identified.
Hope this helps