As far as I can tell from CalTopo, land north of the Missouri, east of Birch Creek, and west of Cow Creek was previously only accessible either via this private land or by approaching from the east and fording Cow Creek here: https://caltopo.com/map.html#ll=47.95479,-109.04672&z=18&b=i...

Anyways, yes, only locked out of the road, not the land.