Soon after Cody Wilson released his plans for the Liberator 3D printable gun, our Critical Making Laboratory undertook to produce a non-functioning version of the gun in order to assess the technical, material, and economic challenges associated with 3D printing proscribed objects. This paper recounts our experiences in creating the gun and analyses the disruptive implications of increasing availability of emerging fabrication technologies for regulation and regulators. 3D printing promises to upend traditional manufacturing by making complex, precision objects easy to produce. Plans are digital and can be duplicated and distributed over the Internet essentially without cost. 3D printers themselves, like their 2D namesakes, are general purpose machines with many legitimate functions, making their regulation a challenge. Some attention has already been paid to what regulators should do and to predicting what they will do. In this paper, we seek to explore what regulators can do. First, a conceptual framework allows us to assess the technological possibilities afforded by 3D printers. Second, we assess the increased regulatory challenge presented by this changed technological infrastructure. It is observed that much effective regulation is accomplished by technical, economic, ethical, and social constraints on action rather than by explicit legal proscription. For example, the high cost of precision machining and high level of technical skill required has traditionally been an effective protection against private individuals producing high-quality firearms ‘under the radar’. Low-cost 3D printers have the potential to allow for the near-effortless creation of precision parts, erasing this ‘contextual regulation’. This paper considers, in broad strokes, several possible regulatory targets: 3D printers, print materials, software, and the design file. For example, 3D printers could be licensed, materials could be watermarked, software could prevent the creation of certain shapes, or designs could carry increased legal culpability for damages or injuries. Against the potential gains to public safety, we weigh the potential costs of regulation that may 1) increase barriers to innovation, 2) unnecessarily restrict or complicate access to general purpose equipment, or 3) be unworkably costly in dollars and person-hours.