Every time talking about guns issues, American politicians and activists would lose their mind. Currently, 3D printers become more and more popular. Somebody uses them to print gun parts, and even an entire gun frame. Politicians and activists intend to block them. Nevertheless, blocking guns printing is very dangerous to our society, so they cannot do that.
The most significant reason why America cannot block gun printing is free and open source software. Aleph Objects is an America based company which produces 3D printers. Their 3D printer has been certified by the Free Software Foundation(http://www.fsf.org/resources/hw/endorsement/respects-your-freedom). It means that, everybody has the freedom to use, share, and modify this hardware's drivers. It also means that, this hardware(3D printers) is very compatible with any free computer operating system, such as GNU/Linux, and well-matched with many different free and open source 3D designing software, such as Blender3D.
What are you talking about? Why it is important? Let's read a copy of the diversity statement of Debian GNU/Linux. This is what Debian GNU/Linux says:
6 No Discrimination Against Fields of Endeavor The license must not restrict anyone from making use of the program in a specific field of endeavor. For example, it may not restrict the program from being used in a business, or from being used for genetic research. (http://www.debian.org/social_contract#guidelines)
If the law block printing guns, it will violate many free software license, such as GPL, BSD, and so on. This kind of license belong to American laws. Therefore, the laws will conflict.
On the other hand, if America blocks printing, but other countries do not block, the States will become weaker and weaker. This situation happened many times in the American history. Normal people do not have gun, because they are willing to follow every law. In contrast, criminals always have opportunity to get guns. Now, they have a new opportunity. Normal people cannot use 3D printers to print guns, but criminals will do that.
Many people believe that, people kill people, guns will not kill people. Therefore, we believe that, 3D printers will never kill people.