Report a legal access block
01A server reports that a legal demand caused it to deny access; the server returning 451 need not be the origin.
The intermediary returns 451. A response-body explanation of the demand is recommended with SHOULD strength.
Source for this drawing: RFC 7725 · Read RFC section 3 ↗
New to this? Start hereA quick picture + helpful background
A message needs an address.
Think of a packet as a small addressed envelope. Devices pass it onward; transport protocols decide what delivery promises an application gets.
Helpful first, if these ideas are unfamiliar
These pictures are analogies to help you learn. The linked RFC explains the actual rules.
Terms in this drawing
- Origin server
- The server responsible for the requested resource.
- Intermediary
- A participant between the client and origin that handles the request or response.
Related RFCs and changes
“Updates” changes part of an earlier RFC. “Obsoletes” replaces it. This list shows selected related documents.
Return 451 for denial caused by a legal demand.
- 451 Unavailable For Legal Reasons indicates that the server is denying access to the requested resource as a consequence of a legal demand. It is not the general status for every access refusal or network failure.
- The server returning 451 might not be the origin server. An entity in the access path can implement the block; a client must not assume that the response came from the publisher.
- A 451 response SHOULD include a response-body explanation of the demand: the party making it, applicable legislation or regulation, and the classes of person and resource to which it applies. This is a recommendation, not a requirement that every legal block be disclosed using 451.
All actors and policy details here are fictional. A client requests /report from a publisher. A filtering intermediary has received a legal demand, stops this access attempt, and returns a 451 explanation instead of forwarding this request. This is one permitted deployment, not a claim that all intermediaries can inspect or modify encrypted HTTP traffic.
Read the RFC section ↗