The npm E451 error occurs when the npm registry blocks a package due to legal or compliance restrictions. This typically affects packages flagged for security concerns or geographic sanctions, requiring you to downgrade or remove the problematic dependency.
The npm E451 error is an HTTP 451 status code that means 'Unavailable For Legal Reasons.' This status code indicates that a package or resource has been blocked by the npm registry or a mirror due to legal compliance, security incidents, or export restrictions. Most commonly, this error appeared when the peacenotwar package was blocked by npm mirrors after a 2022 supply chain security incident. The 451 status code is specifically used when content is unavailable due to legal reasons—not technical issues—distinguishing it from other HTTP errors like 404 or 403. When you encounter this error, it usually means the npm registry has determined the package poses a security risk or violates compliance requirements.
First, look at the full npm error output to see exactly which package is returning the 451 error.
npm installLook for lines like:
ERR! code E451
ERR! 451 Unavailable For Legal Reasons - GET https://registry.npmjs.org/peacenotwarNote the package name and check if it's a direct or transitive dependency.
If the package is a transitive dependency, identify which package requires it. For example, node-ipc versions 9.2.2 and later contained peacenotwar.
Downgrade to a safe version of the parent package:
npm install [email protected]Update your package.json to pin the safe version:
{
"dependencies": {
"node-ipc": "9.2.1"
}
}Then run:
npm installIf you're using an npm mirror, some mirrors may block packages more aggressively for compliance reasons. Switch to the official npm registry:
npm config set registry https://registry.npmjs.org/Verify the change:
npm config get registryThen try installing again:
npm installIf you're using a VPN or corporate proxy, the 451 error might be triggered because your traffic appears to come from a region with restrictions.
npm config get proxy
npm config get https-proxyIf you have a proxy configured and don't need it:
npm config delete proxy
npm config delete https-proxyTry temporarily disconnecting your VPN and running:
npm cache clean --force
npm installThe 451 status code has its origins in Ray Bradbury's novel Fahrenheit 451, which is about censorship. It's specifically used in HTTP standards to distinguish legal/compliance blocks from other types of unavailability. In the npm ecosystem, 451 errors are relatively rare but significant when they occur—the peacenotwar incident of March 2022 affected downstream projects like @vue/cli and served as a major wake-up call about supply chain security. If you're in a country subject to OFAC sanctions, you may experience persistent 451 errors.
npm ERR! code E401 npm ERR! 401 Unauthorized - Token has expired
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npm ERR! code EAI_NODATA npm ERR! errno EAI_NODATA npm ERR! getaddrinfo EAI_NODATA registry.npmjs.org
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npm ERR! code EMPTYPACKAGE npm ERR! Package contains no files
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npm ERR! code EWORKSPACEMISSING npm ERR! Workspace does not exist: packages/missing
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npm ERR! code EADDRNOTAVAIL npm ERR! errno EADDRNOTAVAIL npm ERR! Address not available
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