[txutxu]

There is some reasoning about this on: http://www.451unavailable.org/why-do-we-need-error-451

Still, imho, 4XX could be a response for a given URL, but when "a website is blocked" (from the text of the previous URL), we should go to 5XX, as in 503 - service unavailable.

[eli]

5xx does not really make sense for a single page removed due to DMCA.

[txutxu]

Yes, I don't know if two codes (one for URL and one for the entire site) could make sense in this case.

[orenbarzilai]

does it really matter if it's 5xx or 4xx?

[zackkitzmiller]

Yes. 400 responses are because of client error. 500 responses are for server error.

[jvdh]

Legal restrictions on content are almost always issues on the client side, otherwise they should not be made available at all.

Consider for example the blocking of sites in the UK, or the blocking of the PirateBay website in the Netherlands. Those are all very limited audiences where the location of the client is causing a legal reason why the content can not be displayed.

[gpvos]

541, then?