Error 451: The Government Has Censored This Content

Reason

There is currently no HTTP status code to indicate you can't access content because it's been prohibited by a government agency. Tim Bray, a Google engineer, has proposed the status code "451," in honor of the recently deceased author of Fahrenheit 451, Ray Bradbury, for use when an ISP is ordered by the government to deny access to a certain website. From Bray's proposal:

This document specifies an additional Hypertext Transfer Protocol (HTTP) status code for use when resource access is denied for legal reasons. This allows server operators to operate with greater transparency in circumstances where issues of law or public policy affect their operation.  This transparency may be beneficial both to these operators and to end users…

Responses using this status code SHOULD include an explanation, in the response body, of the details of the legal restriction; which legal authority is imposing it, and what class of resources it applies to.

Blogger Terence Eden first pointed out earlier this month that receiving a "403 FORBIDDEN" notice when attempting to access websites censored by the government is factually inaccurate, since neither the user nor the server are the origin of the error.

Ray Bradbury may not have agreed. From 2007 LA Weekly article:

Now, Bradbury has decided to make news about the writing of his iconographic work and what he really meant. Fahrenheit 451 is not, he says firmly, a story about government censorship. Nor was it a response to Senator Joseph McCarthy, whose investigations had already instilled fear and stifled the creativity of thousands…

[Bradbury] says it is, in fact, a story about how television destroys interest in reading literature. 

The renowned sci-fi writer was no fan of the Internet, either. From a 2009 New York Times article:

"The Internet is a big distraction," Mr. Bradbury barked from his perch in his house in Los Angeles…

"Yahoo called me eight weeks ago," he said, voice rising. "They wanted to put a book of mine on Yahoo! You know what I told them? 'To hell with you. To hell with you and to hell with the Internet.'

"It's distracting," he continued. "It's meaningless; it's not real. It's in the air somewhere."

Nevertheless, whether or not Ray Bradbury agreed, Fahrenheit 451 painted a world of government censorship we're probably closer to today than we were in 1954, and internet censorship is real censorship. 

Reason on Ray Bradbury as an enemy of the state