That's right. It is notifying the request that the server blocked this information because of
CENSORSHIP of the information mandated by the legal system!
This is really a good thing. Here in Australia they block all kinds of stuff arbitrarily with no explanation and you simply get a timeout. No explanation, no rationale. The 451 code in the response will help people to realise that the morons who work in government jobs are just flipping coins up there to decide what gets through their bandwidth pipes.
I kept getting blocked last year trying to read up some more on the Irish Potato famines and for the life of me had no idea why certain governments would block two century old history. It just didn't make any sense.