On 2nd August, the Center for International Strategic Studies published an article saying that 3D printing technology allows the manufacturing of metal-free guns that are nearly impossible to identify with metal-detection security measures. Understanding how and why export controls have taken on such a central role in the debate over 3D printing of guns is critical to understanding what the Trump administration’s policy reversal means, and what its implications may be in the years ahead. The article set out the current situation under US laws.
https://www.csis.org/analysis/fired-over-firearms-how-do-export-controls-relate-3-d-printing-guns