Leaders from across the globe will gather in Washington from March 31 to April 1 for the fourth and final Nuclear Security Summit. They will discuss multilateral efforts to prevent nuclear terrorism and the smuggling and proliferation of nuclear materials. There are a number of things that all can agree on. Among them, that nuclear weapons in the hands of sub-state actors is a bad thing and that safeguards should be taken to ensure the security of nuclear arsenals in states where political stability cannot be taken for granted. But, as with most summits of this nature, this gathering will not bring about enforceable measures on a multilateral level. The real substance to be found at the summit will emerge from the meetings taking place on the sidelines....