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HTTP 451 Unavailable For Legal Reasons

HTTP 451 Unavailable For Legal Reasons means the resource is blocked for legal reasons, such as a court order or sanctions. The request contains an error or can’t be fulfilled. Retrying unchanged won’t help.

Class
4xx Client error
Standard
RFC 7725
Cacheable by default
No
Safe to retry
No
Go constant
http.StatusUnavailableForLegalReasons

What HTTP 451 means

The number is a nod to Ray Bradbury’s Fahrenheit 451. Use it when content is blocked by law in the user’s jurisdiction, for example a court order, DMCA takedown or GDPR geo-blocking. The Link header can point to the authority that demanded the block.

Retrying

No. Fix the request first; sending it again unchanged will get the same response.

Example response

HTTP/1.1 451 Unavailable For Legal Reasons
Date: Wed, 21 Oct 2026 10:30:00 GMT
Link: <https://authority.example/order>; rel="blocked-by"
Content-Type: application/json

How to return 451

Node.js (Express)
res.status(451).json({ error: 'Unavailable For Legal Reasons' });
Python (FastAPI)
from fastapi import HTTPException

raise HTTPException(status_code=451, detail="Unavailable For Legal Reasons")
Go (net/http)
http.Error(w, http.StatusText(http.StatusUnavailableForLegalReasons), http.StatusUnavailableForLegalReasons)
nginx
location /private/ {
    return 451;
}

Related status codes

  • 403 Forbidden : The server understood the request but refuses to authorize it.
  • 404 Not Found : The server can’t find the requested resource.
  • 410 Gone : The resource was deliberately removed and won’t come back.

Other 4xx status codes

400 Bad Request · 401 Unauthorized · 402 Payment Required · 403 Forbidden · 404 Not Found · 405 Method Not Allowed · 406 Not Acceptable · 407 Proxy Authentication Required · 408 Request Timeout · 409 Conflict · 410 Gone · 411 Length Required · 412 Precondition Failed · 413 Content Too Large · 414 URI Too Long · 415 Unsupported Media Type · 416 Range Not Satisfiable · 417 Expectation Failed · 418 I’m a Teapot · 421 Misdirected Request · 422 Unprocessable Content · 423 Locked · 424 Failed Dependency · 425 Too Early · 426 Upgrade Required · 428 Precondition Required · 429 Too Many Requests · 431 Request Header Fields Too Large · 444 No Response · 499 Client Closed Request

See the full list of HTTP status codes.

Sources

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Frequently asked questions

What does HTTP 451 Unavailable For Legal Reasons mean?

HTTP 451 Unavailable For Legal Reasons means the resource is blocked for legal reasons, such as a court order or sanctions. The number is a nod to Ray Bradbury’s Fahrenheit 451. Use it when content is blocked by law in the user’s jurisdiction, for example a court order, DMCA takedown or GDPR geo-blocking. The Link header can point to the authority that demanded the block.