"At least four terrorist groups, including Al Qaeda, have demonstrated interest in using a nuclear device. These groups operate in or near states with histories of questionable nuclear security practices. Terrorists do not need to steal a nuclear weapon. It is quite possible to make an improvised nuclear device from highly enriched uranium or plutonium being used for civilian purposes. And there is a black market in such material" (Brill and Luongo)
If terrorist groups or rogue nations got their hands on nuclear weapons, it could mean big trouble for countries around the world. These communities do not ratify to treaties addressing things like nuclear weapon non-proliferation or nuclear weapon testing rules.