Before joining Constitutional Accountability Center, Si was Public Policy Counsel to the National Senior Citizen Law Center. Si served as Associate Director of President Jimmy Carter’s White House Domestic Policy Staff (1977-81), as a partner in Powell, Goldstein, Frazer, and Murphy LLP (1981-2002), and as Senior Counsel to Sidley Austin LLP (2002-2006). He is a Trustee of the Center for Law and Social Policy and a member of the Administrative Conference of the United States.  His articles have appeared in the Atlantic, the Washington Post, The American Prospect, Roll Call, Slate, The Hill, Newsweek/ Daily Beast, Politico, The New Republic, the Huffington Post, as well as law reviews. Si writes frequently for the American Constitution Society’s ACS Blog and has published several ACS issue briefs, including “Mandatory Health Insurance: Is It Constitutional?”, which was released during the Senate health care reform debate in December 2009, and "The Health Reform Lawsuits: Unraveling a Century of Constitutional Law and the Fabric of Modern Government," published in February 2011. His Atlantic article, “The Most Dangerous Branch?”, has been republished in two anthologies, The Best American Political Writing 2003 Royce Flippin, ed. (Avalon Press 2003), and Principles and Practice of American Politics: Classic and Contemporary Readings, 2d ed., Samuel Kernell and Steven S. Smith, eds. (CQ Press 2003). He graduated from Yale Law School, where he was Note & Comment Editor of the Yale Law Journal.