This decisions are being made by mid-level beauraucrats that don't want to make an effort to learn about what they're deciding. I'd say we should make them work --- start filing FOIA (Freedom of Information Act) requests to Department of Interior, National Park Service, and the Fish and Wildlife Service asking for all documents pertaining to their policies on geocaching, documents pertaining to the development of such policies, documents pertaining to legal interpretations of geocaching, documents pertaining to any prosecutions of individuals for participating in geocaching, etc. (You might want to ask for the same documents for hide-and-go-seek, since this is basically just a variant of that game). By law, each FOIA request must be filled within a certain period of time. There are several exemptions to the FOIA that allow one to have these requests filled at no cost. FOIAs are the biggest pain in the a** for my agency, I'm sure it is for DOI also.
Furthermore, if I have this right, neither the NPS, BLM nor USFS can actually ban geocaching without going through a rule making process, open for public comment, and published in the Federal Register. The process may be opposite for USFWS, where they have to publish permissable new uses of their lands in the Federal Register and open those up for public comment.