Summary: The US Justice Department has made a lot of decision on how to use 3D to print a gun. The first 3D gun was printed in 2013 and the document how to print had been downloaded for thousands times. The US Justice Department has now said that Americans may "access, discuss, use and reproduce" the technical data. Since that the way how to get the gun become more cheaper and better. Therefore, it has a lot of influence one that.