Documents on the Laws of War, co-edited with Richard Guelff, (Clarendon Press, 1982, 2nd ed., 1989, 3rd ed., 2000).
United Nations, Divided World: the UN's Roles in International Relations, co-edited with Benedict Kingsbury, (Clarendon Press, 1988, 2nd ed., 1993).
Hugo Grotius and International Relations, co-edited with Hedley Bull and Benedict Kingsbury, (Clarendon Press, 1990).
The United Nations Security Council and War: the Evolution of Thought and Practice since 1945, co-edited with Vaughan Lowe, Jennifer Welsh and Dominik Zaum, (Oxford University Press, 2008).