A 27-year-old man has been arrested in Kawasaki, Japan, on accusations of possessing several 3D-printed guns, according to local news reports.

Yoshitomo Imura allegedly downloaded and printed five plastic guns, two of which could fire real bullets. He was arrested last month, but the news was only revealed on Thursday. It's believed to be the first arrest made for possession of 3D-printed guns in Japan, a country with extremely strict gun laws. A law passed in 1958 forbids a person from possessing a "firearm or firearms or a sword or swords," although it lists list several exceptions. (Guns were used in only seven murders in Japan — a nation of about 130 million people — in all of 2011.)

Imura defended himself, saying he didn't know it was illegal to own a plastic gun.

“I produced the guns, but I didn’t think it was illegal," Imura said, according to Japan Times. "I can’t complain about the arrest if the police regard them as real guns."

The man allegedly uploaded videos of his guns online; in one video, a person who appears to be Imura assembles and fires off one of his 3D-printed guns with blank bullets "to protect the laws of Japan," a caption in the video reads.

The police seized the five guns and also found 10 toy guns in Imura's apartment. The authorities also seized his 3D printer, but didn't find any live ammunition at his apartment.

On Twitter, Imura has previously defended the right to possess guns, according to public broadcaster NHK. "Gun restrictions are violation of human rights," he once tweeted.

One of Imura's guns is the Liberator, the world's first 3D-printed gun, designed by American law student Cody Wilson. Last year, Wilson manufactured and fired the Liberator for the first time. The U.S. State Department later forced him to remove the digital blueprints of the gun from the his site DefCad, but at that point, they had been downloaded hundreds of times and reposted on several other websites.

In the U.S., it's illegal to manufacture a 3D-printed gun if it can't be spotted by a metal detector, but there are no specific regulations on 3D=printed guns.

BONUS: Mashable Explains: 3D Printing