From The Washington Free Beacon:

Amazon banned the sale of a gun book on Wednesday night for an unexplained violation of the company’s rules.

The listing for The Liberator Code Book: An Exercise in Freedom of Speech, which had been available on Amazon since Aug. 1, was removed from Amazon’s website. The web address where the book had previously been listed now redirects to an error page. The web address where a Kindle book titled The Liberator: An .STL File Published as a Book also now redirects to an error page.