From The Washington Post:

The ability to “print” or manufacture guns privately will allow individuals to bypass background checks, the primary way that guns are regulated today. And that challenge will expand exponentially as the technology advances, one day enabling individuals to print chemical, biological and nuclear weapons of mass destruction at home.

The threat of privately printed weapons will soon grow beyond the lethal handguns now in circulation. As we argue in research forthcoming in the October issue of the Journal of Policing, Intelligence and Counter Terrorism, considering expected advances in the technologies, terrorist groups will threaten nations with 3-D printed chemical, biological and nuclear weapons within a couple of decades.