Rip it up and throw it in their faces.
Then get ready for the arrest.
F ‘em.
Alas, THAT is actually a crime, whereas it is highly debatable if the national parks can actually close without violating federal law, or if national parks officials (or rangers) have the legal ability to deem you trespassing on public land for anything other than an actual emergency (forest fire, mudslide, active police investigation or public health hazard.)
So feel free to engage in debate, but don't litter.
See ya'll on the Group W bench.