They can take the plans for a plastic gun off the web but leave up plans on how to build a pressure cooker bomb?
When they figure out how to print with graphene, and they will, we should worry about the printing of real guns. Graphene is substantially stronger than steel and much lighter.
A hypothetical one-square-meter hammock made of graphene would be strong enough to support a four-kilogram cat (8.82 lbs.), according to Swedish physicist Per Delsing. The hammock itself, just one atom thick, would weigh roughly one milligram—about the same as one of the cat’s whiskers. The Warsaw Voice Online, November 2, 2010
Once they figure out how to make 3D bonding take place, you will have a material that is stronger than diamonds.
Seems like a lot of work to get a cat in a hammock.