Hi Tim. Awesome choice of the error code. May be you could ammend it to include some sort of reference to the censored data like this:

451 Unavailable for Legal Reasons of Resource magnet:?xt=urn:ed2k:354B15E68FB8F36D7CD88FF94116CDC1&xl=10826029

That way would be more transparent what is being censored if providing that info is not also censored. 😉