The case law would seem to indicate that Congress was granted the power to act as it sees fit regarding these lands, and divestiture would be possible only by legislation.
Fascinating body of court decisions stretching back to
our treaties with Spain, France and Mexico govern land sovereignty, and I’ve wasted several hours looking at
court decisions.
I did find a nice article on the Property Clause of the Constitution on the Heritage website.
http://www.heritage.org/constitution/#!/articles/4/essays/126/property-clause
Another essay:
http://www.law.umaryland.edu/marshall/crsreports/crsdocuments/RL34267_12032007.pdf
It is a very interesting legal case and Bundy appears to be in the wrong. However, the tremendous show of force is unconscionable. It’s hard to argue against Bundy when the feds won’t lift a finger to remove illegal alien trespassers from land that doesn’t belong to them but use such force against freeping cows.