[3][4] Carter was a founding member of Iraq and Afghanistan Veterans of America, and he also served as a principal of the Truman National Security Project.

[citation needed] He was senior fellow and counsel at the Center for a New American Security, and director of the CNAS research program on the Military, Veterans & Society.

In 2011, Carter left McKenna to join Caerus Associates, a strategy and design consulting firm in Arlington, Virginia, as the company's Chief Operating Officer and General Counsel.

[10][11] Carter's articles have appeared in many other publications, including the New York Times, Washington Monthly, Wall Street Journal, and Chicago Tribune.

The Washington Post reported in February 2009 that Carter was slated to be the new Deputy Assistant Secretary of Defense for Detainee Affairs, following speculation on Pentagon blogs about his appointment.

Carter was the chief architect of the Obama administration plan to close Guantanamo Bay, and bring detainees to a maximum security prison in Northwest Illinois.

His last official trip was to Thomson, Illinois, the site of a prison the Obama administration has decided to use to house some captives currently held in detention in Guantanamo, in Cuba.