As far back as World War 1 there were concerns that transmission of data over the telegraph could result in the loss of military secrets. The advent of the internet saw these fears expanded, with digitalisation of component design becoming commonplace. In parallel, two further trends in manufacturing have been observable. First, manufacturing capability has become increasingly dispersed and simplified with the availability of automated manufacturing equipment, such as Computer-Numerically Controlled (CNC) machine tools . This trend has not lessened the expertise required to manufacture an item. Instead, the expertise required to design a component continues to be heavily centralised, requiring years of engineering training, thus leading to the second tend. The second trend is for ‘knowledge’ to be packaged up into Computer Aided Manufacture (CAM) files which can be dispatched electronically to the CNC machine anywhere in the world for machine operators to run.
Recent advances in additive manufacturing (more commonly referred to as 3D printing technology) bring this discussion to the fore. Designs now exist for guns designed by specialists but which can be printed by anyone with a suitable printer simply by downloading the CAM files .
Distribution of fire arms within a country’s borders is a matter for that country’s law makers and law enforcers, not for the international export control regimes. Nonetheless, 3D printing combined with the availability of information through the internet challenge the division between national and international jurisdictions. Exports of intangible technology are difficult to police. Illicit transfers of controlled dual-use technologies while more difficult for customs officials to detect than say a main battle tank can nonetheless be spotted at a country’s border. Intangible technology transfers cannot generally be detected at all as governments generally have no capability to monitor electronic transfers between companies or/and individuals, governments usually have little proactive capacity to audit firms to ensure management processes on intangible technology controls are in place, and governments have almost no ability to verify whether a transfer of technology has taken place by visiting the recipient.
Should the international export control regimes control the transfer of 3D printers? The precedence is with CNC machinery. Presently, highly-accurate and multi-axis machinery is controlled by the Nuclear Suppliers Group and the Wassennar Arrangement principally because this subset of machinery can be used to manufacture highly-specified components for use in military and nuclear applications. Presently arms, and technology and software associated with the production of arms, are controlled by the Wassennar export control regime. The materials used in current 3D commercial printing are generally have low melting points or are fused together using glues or other binding agents. While such materials can have uses of concern, in general current manufacturing techniques allow items to be manufactured from these materials with a little manufacturing skill. For example, while 3D printing may make creating parts with complex geometry as simply loading ink cartage and a CAM file; most parts could be made utilising machine tools and hand tools by an individual with prerequisite skills and equipment. Certain more advanced categories of 3D provide greater utility. For example, advanced and experimental techniques allow metals and DNA to be printed. If the precedence with the CNC machine tools hold true, specialist 3D printers should be controlled if the equipment poses a clear risk of use in proliferation of WMD or advanced military capabilities subject to the following evaluation criteria 
• Foreign availability outside Participating States.
• The ability to control effectively the export of the goods.
• The ability to make a clear and objective specification of the item.
• Controlled by another regime.
Custom-designed machines that could print DNA or metals would be considered advanced even today. The manufacturing of such equipment is likely to be highly concentrated in a handful of countries and firms for some time to come. Even for CNC machine tools, few companies manufacture the controllers required for multi-axis machine tools even though the manufacturing base for machine tools is increasingly dispersed. For current commercially-available 3D printers the manufacturing base is potentially huge. With the exception of motors, controllers and related parts, 3D printers can reproduce themselves. Almost all of the components can be purchased from a standard electronics catalogue retailer by anyone other than a ‘designated entity’ . The materials used in 3D printing are also ubiquitous with even high street stationary stores stocking supplies. There are exceptions. Parts made of fully-fluorinated materials (PTFE etc) have uses in uranium enrichment and reprocessing, for example. However, standard thermoplastic could not be used for these purposes and those materials that could be used in such specialist applications may be controllable in their own right. Nonetheless, even after building a 3D printer from parts procured from the marketplace, the operating systems are more specialist. A user could not code their own operating system and would need to download the operating platform.
Could authorities control the transfer of ‘know how’ associated with the production of items of concern? This could potentially be achieved in two ways, with the first perhaps being more practical than the second. First, by controlling designs patterns for specific items of concern, such as guns. Precedence exists for this. Export control regimes typically control “technology”, which is comprised of both the physical goods and associated design information. This can required individuals or firms to apply for licences before sending emails, carrying documents and laptops overseas, or potentially even calling a customer. This approach intends to restrain the transfer for ‘explicit’ rather than ‘tacit’ knowledge, with consultancy delivered in person at a customer’s site potentially being exempt. For example, the British government states “you don’t need a licence for what’s in your head”.
Such ‘explicit’ information may be available on the internet , but such information tends to have commercial value, thus driving protection. The process of making this information available on the internet is typically a crime. For guns, military equipment, and controlled dual-use technology, controls on intangible technology already exist. Likewise, bomb designs can be found online but few individuals will go searching as this in itself is typically illegal and may result in an increased likelihood of the criminal intent being detected by the authorities. There are challenges with this approach. For one, unlike most controlled goods which are complex because of their metallurgy, electronics, or software, basic 3D printed products are not. The ubiquity of material means that the design could be replicated simply by scanning the components of a printed product. Thus barriers to reproduction are low.
Second, it is perhaps possible to control the operating system for 3D printers in a similar way to the patterns themselves. There are multiple challenges to this approach. It would directly constrain the development of 3D printing, which promises to be an empowering technology. It also lacks resilience given that anyone with a printer potentially could copy the code embedded in the printer. It’s also not clear what the objective of control would be: would authority be given to legitimate end users to use the equipment and if so, how given the ubiquity of components that could be made, how would the risks be assessed?
Individuals intent on acquiring guns and countries intent on acquiring WMD may well succeed given sufficient effort. The aim of the international community is to detect and where appropriate frustrate acquisition, perhaps for long enough for some legal or enforcement action or societal change to be taken to end the pursuit. 3D printing has the potential to allow such actors manufacture components and equipment with less training and expertise. Nonetheless, there are steps the international community in general and national authorities in particular can take to manage the risks. Items specifically designed or prepared for a military or WMD end use should be controlled. These controls must be enforced to deter evasion of current controls. Developments in more advanced printers should be monitored for potential addition to control lists.
 CNC machine tools perform machining operations on an object in accordance with pre-written instructions. The machine tool operator must simply load the material into the machine then start the programme.