content: If it is public land then it is governed by the laws established for public use. These tend to include things like no camping, starting fires, or littering. As such these people are probably violating all of them.  If it is private land, then activity is restricted per the desires of the owner, so then these people are trespassing. Just because land is there, regardless of being public or private, doesn't mean people have unrestricted rights to its usage.