Isn't it quite close to both 403 Forbidden, "request was a legal request, but the server is refusing to respond to it" and 401 Unauthorized? And now it's on the wikipedia http://en.wikipedia.org/wiki/HTTP_status_codes , and that equates with being approved, right?
TIL Microsoft uses 450 for parental control. And now 451 for legal censorship. Perhaps we could use the 450-459 range to signify various censorship scenarios. The 450s is also a nice middle ground between 400s and 500s.
The argument against 403 is that the server might not get to the resource at all, so it doesn't get a chance to refuse the response. A router with filtering capabilities might also terminate the connection and return 451 if the target server is censored and won't be reached. (wether that's practically likely to happen—e.g., at the Great Firewall, or for ICE seizures—is a different matter entirely)
