Associate Professor, Duke University Law School. This is a revised and condensed version of a report commissioned by the Simons Centre for Peace & Disarmament Studies, University of British Columbia, and presented to the House of Commons Standing Committee on Foreign Affairs & International Trade, 6 May 2002. I am grateful for comments from Robert Adamson, Lloyd Axworthy, Gerry Barr, Douglas Bland, Bruce Broomhall, Jutta Brunnee, Maurice Copithorne, Paul Evans, John Godfrey, David Haglund, Brian Job, Nicole LaViolette, Neil MacFarlane, Patricia Marchack, Pierre Martin, Donald McRae, Richard Price, Rene Provost, Ernie Regehr, Marco Sassoli, Jennifer Simons, Penelope Simons, Stephen Toope, and Michael Wallace.IN JANUARY 2002, IT BECAME APPARENT that negotiations were under way to place a substantial part of the Canadian armed forces - land and sea forces as well as air - under the operational control of a permanent, integrated command structure under United States leadership.(1) The creation of a 'Northern Command' in April 2002 unified the continental United States into a single military command and provided a logical precursor to an expansion that would include Canada and Canadian forces.(2) A number of difficult questions will have to be answered before the Canadian government could responsibly embark on closer military co-operation of this kind.UNITED NATIONS/NATO/NORAD OPERATIONSCanadian soldiers have in the past functioned under United States command in operations authorized by the United Nations, the North Atlantic Treaty Organization (NATO), and in the North American Aerospace Defence Command. The first operation authorized by the United Nations Security Council was the 1950 intervention in Korea. Subsequent operations include the 1991 Gulf War and the intervention in Bosnia-Herzegovina in 1991-5. Canada has also placed its soldiers under foreign command within peacekeeping operations authorized by the General Assembly. Those operations are not contentious: the Council and the Assembly operate under the United Nations Charter - a multilateral treaty ratified by 190 states. Although American commanders are sometimes in charge of day-to-day operations, they have the explicit, delegated authority of the international community behind them. And these operations are, in any case, temporary in scope.As parties to the 1949 North Atlantic Treaty, Canada and the United States are obligated to assist any NATO member country subject to an armed attack. This obligation, set out in article 5, has been invoked only once - by the United States following the 11 September 2001 attacks in New York and Washington. Even then NATO was not called upon to engage in military action. Article 5 operations would be very different from that which is contemplated today. NATO structures remain largely dormant and without authority, except in those specific instances in which the members agree to activate them. Moreover, NATO, like the United Nations, is a multilateral organization - in this case composed of 19 states. When an American commander is placed in charge of an operation, he acts as a NATO commander within the multilateral structure.Outside the context of article 5, NATO participated in operations authorized by the Security Council in Bosnia-Herzegovina. And in one instance - Kosovo - NATO acted without explicit United Nations approval. But even then, the operation was that of a multilateral organization, subject to its authorization and control. Every target had to be approved unanimously by all involved governments.NORAD was designed to enable rapid responses to incursions into Canadian or United States airspace by Soviet bombers. Its integrated command structure is limited to one specific function - air defence - and involves a relatively small part of the Canadian forces. Since the end of the cold war, the number of Canadian planes and pilots required for NORAD duties has decreased. And pilots on intercept missions do not encounter many of the legal issues faced by ground and naval personnel, since they do not, for example, take prisoners or lay mines. …