Reviewing decades of sanctions on Iran, the authors write that a diplomatic resolution should be the approach to resolving the standoff with Iran over its nuclear program. Any form of negotiated settlement will require sanctions relief, notably from the United States, the European Union, and the United Nations Security Council. But what, exactly, are the mechanics involved in removing these sanctions? The authors write that the most difficult sanctions to lift are US congressionally imposed measures. President Barack Obama, they write, must overcome the obstacles in his path should the time arrive to begin reversing sanctions.