One can get to the site of the Forks (it did burn in 2012) in the summer with a variety of vehicles, but it's a rough gravel/dirt road.
Beyond the roadhouse are a variety of 4x4 roads/trails, including the main "road". Some of these trails do cross private property and could rightfully be blocked off...but the only blocking I've ever seen is on the main road and that, as pointed out above, is not legal. However, it isn't hard to end up on a miner's claim or other private property.
All in all, I would only recommend going beyond the roadhouse with any 4x4 vehicle if you had all the gear to get unstuck: Chainsaw, winch, handyman jack, shovels, rigging gear, etc. A quad or UTV would be better.