Even non-repressive regimes can impose harsh penalties to limit the spread of certain information. The United States couldn’t stop WikiLeaks from distributing secret diplomatic cables, but it did manage to strike a terrible blow to the group when it cut off its funding sources. In the same way, by imposing strict penalties for the distribution and possession of child pornography, Western governments have severely limited its spread online.The rise of file-sharing seems to support the 3-D gun movement’s claims—people share movies and songs illegally online, and no government has been able to stop them. But note that doing so isn’t completely safe; if the authorities set their mind to it, they can bankrupt you for sharing songs online. Countries where guns are already strictly curbed could impose similarly harsh measures against the distribution of plans for 3-D guns—and if they enforce them strictly, they might well limit their availability.
To the extend Mr. Manjoo is basing these arguments on U.S. law, the analogies to crackdowns on pirated music / movies and child pornography are way off-base.
First, the analogy to piracy fails because there will be no copyright issue. Mr. Wilson and his kind will be distributing these plans, which are their own intellectual property, freely and without restriction. It is only copyright law that prevents distribution of movies and music, and it is only copyright that allows the government to enforce the standards Mr. Manjoo mentions. Given that there will be no copyright on these gun-printing blueprints, no one will have the legal right to prevent their distribution. Congress would need to pass a law to make such plans illegal, but that law would almost certainly be unconstitutional under the 1st Amendment, the 2nd Amendment, or both.
Second, the child porn analogy fails for a similar reason. Laws preventing dissemination of child porn are allowed on a very narrow exception to the First Amendment, and there is no reason to believe that dissemination of these gun-plans would fit any exception.
That is not to say the U.S. government is without recourse. In fact, it's already taking action. The U.S. State Department wrote Mr. Wilson a letter demanding that he take the plans down from his website on the theory that they may violate export regulations under certain arms control treaties. Mr. Wilson has complied with the request pending the State Department's review, although he believes that the regulations do not apply to his non-profit enterprise. This also raises issues whether the government can regulate anything published on a website as an "export" and whether treaties pertaining to exports can override constitutional rights. But we'll leave those questions for another day. I will just note that you can buy the "Anarchist Cookbook" on Amazon.