This request may not be serviced in the Roman Province of Judea due to the Lex Julia Majestatis, which disallows access to resources hosted on servers deemed to be operated by the People's Front of Judea.
The use of the 451 status code implies neither the existence nor non- existence of the resource named in the request. That is to say, it is possible that if the legal demands were removed, a request for the resource still might not succeed. Note that in many cases clients can still access the denied resource by using technical countermeasures such as a VPN or the Tor network. A 451 response is cacheable by default; i.e., unless otherwise indicated by the method definition or explicit cache controls; see [RFC7234]. 4. Identifying Blocking Entities As noted above, when an attempt to access a resource fails with status 451, the entity blocking access might or might not be the origin server. There are a variety of entities in the resource- access path which could choose to deny access, for example ISPs, cache providers, and DNS servers. It is useful, when legal blockages occur, to be able to identify the entities actually implementing the blocking. When an entity blocks access to a resource and returns status 451, it SHOULD include a "Link" HTTP header field [RFC5988] whose value is a URI reference [RFC3986] identifying itself. When used for this purpose, the "Link" header field MUST have a "rel" parameter whose value is "blocked-by". The intent is that the header be used to identify the entity actually implementing blockage, not any other entity mandating it. A human readable response body, as discussed above, is the appropriate Bray Expires May 8, 2016 [Page 4] Internet-Draft HTTP-status-451 November 2015 location for discussion of administrative and policy issues. 5. Security Considerations Clients cannot rely upon the use of the 451 status code. It is possible that certain legal authorities might wish to avoid transparency, and not only demand the restriction of access to certain resources, but also avoid disclosing that the demand was made. 6. IANA Considerations The HTTP Status Codes Registry should be updated with the following entry: o Code: 451 o Description: Unavailable for Legal Reasons o Specification: [ this document ] The Link Relation Type Registry should updated with the following entry: o Relation Name: blocked-by o Description: Identifies the entity blocking access to a resource folllowing on receipt of a legal demand. o Reference: This document 7. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ RFC2119, March 1997,