The restrictions on what the state can ban are only valid inasmuch as they protect fundamental right. The supposed right to 3D printers is not fundamental, but is derived from a right to own good things, if they are available. If the state can provide an alternative that yields similar benefits it does not actually infringe any fundamental right by banning their domestic use. For example, industrial 3D printed manufacturing also provides cheap and innovative products. On the other hand, the potential harms of domestic printers are exponential, and we do not have a right to anything that causes harm to society. The state therefore has a mandate to ban 3D printers in households.