From one of the authors of the original paper:
It is true that there have been a number of proclamations diminishing monuments in the past but none of these have been challenged in court so no court has ever passed on the legality of these actions. Moreover, all of these actions were pre-FLPMA, which matters significantly here because FLPMA repealed the Midwest Oil decision. A 1935 Solicitor’s Opinion relied heavily on Midwest Oil to justify proclamations that diminished monuments. Post FLPMA, that justification is gone.
Original post here.
House Resources staff response.