Please do not hike into Corkscrew Canyon without stopping by the Furnace Creek Visitor Center and asking a park ranger for permission to do the hike.
Are the Park Rangers able to grant legal access to Corkscrew Canyon on behalf of Rio Tinto Mining? The no trespass sign was up when we visited the canyon in March, 2016. We ignored it. I suspect that it is really a transfer of liability. If a hiker is injured, they can't sue Rio Tinto because the area is closed. Similarly, the road closed sign on the Whitney Portal Road in winter is routinely ignored by winter mountaineers. If one of their cars is buried in an avalanche, they can't sue Inyo County because the road was closed.
By the way, we normally are great respecters of private property, but not for an outfit like Rio Tinto. They deserve no respect. See here for a list of their numerous abuses:
www.corp-research.org/rio-tinto