Learned via the website Kotaku of some bad news from Japan, the (as far as I know) first arrest of a human being for possessing a plastic weapon made via a 3D printer:

A twenty-seven year old Japanese man was arrested on suspicion of printing and possessing guns. This is the first instance of such an arrest being made in Japan….. According to ANN News, Yoshitomo Imura allegedly downloaded gun blueprints from a foreign site and then printed the resin guns with his 3D printer. Imura had apparently uploaded videos to YouTube in which he fired off what looks to be a 3D printed pistol. Last month, police seized five 3D printed guns from Imura's Kawasaki City home…. It is possible to own guns in Japan, but the country has incredibly strict firearms regulations.

Cody Wilson, the most prominent American proponent and innovator of 3D printed weaponry, had this to say on his Defense Distributed Blog:

I have often been asked who the first person to be arrested for 3D gun printing would be. My answer was the creative and curious. Yoshitomo Imura is a person of strong character and virtue under unfavorable circumstances. He expressed with his work only virtue, but this virtue is ostracized by his society. He performed his work in the open, without suspicion, fear or dishonor. That he must harvest persecution and calamity for his creative and intrepid instincts is an indictment of his tame and mediocre society. Yoshitomo Imura is trying to say something profound.- is trying to be profound. I hope Mr. Imura's attitude to his instincts is not reversed by the tomb-like atmosphere which will now cloud his life.

I profiled Wilson in a feature in the December 2013 Reason.

Reason TV interviewed Wilson more recently: