I just saw this. The Forest Service, which is a whole different agency than the Park Service--Forest Service is under Dept. of Agriculture, Park Service is Dept. of the Interior, is considering changing their rules on ebikes and is soliciting comments. Here is the link. At this time, the USFS considers ebikes to be motorized and does not allow them on bicycle trails.
Forest Service Manual 7700 Travel Management; Chapter 7700, Zero Code; Chapter 7710 Travel Planning
The United States Department of Agriculture (USDA), Forest Service, is proposing to revise its directives to update and clarify guidance on management of electric bicycle (e-bike) use on National Forest System (NFS) lands. E-bikes have become increasingly popular nationwide among outdoor...
www.federalregister.gov