here's the law wrote:
36 CFR 4.30(g)Other requirements.
(2) Unless specifically addressed by regulations in this chapter, the use of a bicycle within a park area is governed by State law. State law concerning bicycle use that is now or may later be in effect is adopted and made a part of this section.
(h)Prohibited acts. The following are prohibited:
(4) Operating a bicycle abreast of another bicycle except where authorized by the superintendent.
The superintendent has indicated (though the media won't cover it) that there was NO such authorization. State law (Tennessee) is also clear.
Funny how the only LRC people who cite laws (and facts to some extent) seem to favour the driver's side of things, while OTOH those who cite media bloviation favour the cyclist.