Does the thing being bypassed prevent you from saving the page, or from making in any other way a copy of any content you've already fetched?
If not, how could it be classed as copy-protection?
Edit: One other thing: if spoofing UA headers was a problem, all the browsers in the world would fall foul of it - because non-Mozilla browsers all say that they're Mozilla, and Opera said it was IE, and Chrome said it was Safari, and now a bunch of browsers say they're Chrome - at the same time as saying they're Mozilla. Except it's more complicated than that.
this is basically the "computer scientist" view of the world in https://ansuz.sooke.bc.ca/entry/23, especially the Monolith bit. spoofing UA could be legal in general or when done for interoperability but illegal when done with intent to bypass access control.
If not, how could it be classed as copy-protection?
Edit: One other thing: if spoofing UA headers was a problem, all the browsers in the world would fall foul of it - because non-Mozilla browsers all say that they're Mozilla, and Opera said it was IE, and Chrome said it was Safari, and now a bunch of browsers say they're Chrome - at the same time as saying they're Mozilla. Except it's more complicated than that.