In a recent piece in the Washington Post, Professor Mary Dudziak drew attention to the Executive Branch’s continued reliance upon President Truman’s police action on the Korean Peninsula as a “precedent for the unilateral presidential power exercised today.” However, the current legal significance of the Korean precedent is more limited than some critics of presidential unilateralism might fear or advocates for such power may hope. These limitations have significant implications for ongoing war powers debates.
Under the Executive Branch’s own longstanding views, at least two constitutional provisions constrain the scope of the President’s authority to initiate the use of force without prior congressional authorization. Taken together, the Take Care and Declare War Clauses reduce the utility of the Korean War as a precedent supporting the initiation of large-scale uses of force by the President.
Article II, Section 3 of the Constitution requires that the President “take Care that the Laws be faithfully executed.” As I explain in a forthcoming article in the Cornell Law Review, the understanding that treaties, including the U.N. Charter, are “Laws” not only is a deeply rooted Executive Branch position, but also was a key element of the Truman Administration’s argument for the use of force on the Korea Peninsula in the absence of prior congressional authorization. In a 1951 legal memorandum submitted to the Senate, the Truman Administration explained, “the President has the authority and the duty to carry out treaties of the United States. Treaties, duly approved, are the laws of the land and it becomes the President’s duty ‘to take care that they be faithfully executed’ as laws.” Consequently, the President is “under a duty to see that the great objectives of the Charter are carried on so far as it lies within his power to do so.”
Whether or not the Truman Administration properly relied upon the Charter as a source of domestic legal authority in using force on the Korean Peninsula, the acknowledgment that the Charter is binding law that the President is obligated to execute faithfully necessarily entails constraints upon the President’s constitutional war powers. Specifically, Article 2(4) of the Charter provides in relevant part that “[a]ll Members shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state.” The United States has recognized only three exceptions to Article 2(4)’s prohibition on the use of force: (1) Chapter VII authorization from the U.N. Security Council; (2) self-defense; or (3) consent of the territorial state. (The United States has famously declined to adopt the doctrine of humanitarian intervention.)
Thus, as Professor Marty Lederman has argued, Article 2(4) imposes constitutional limitations on the President’s powers under Article II. Truman’s actions to help repel armed aggression against the Republic of Korea were consistent with Article 2(4), as the use of force could be justified at the very least on the basis of collective self-defense (and potentially also on the grounds that it was authorized by the Security Council under Chapter VII of the U.N. Charter). However, if in contrast to the Korean precedent, a President unilaterally directed the use of force outside of the three exceptions identified above, such action would not constitute “faithful execution” of Article 2(4). The Korean precedent and its “Take Care” justification cuts against the argument that the President has unilateral authority to use force in violation of the U.N. Charter.
The Declare War Clause imposes a further constraint on the President’s war powers. Following the Truman presidency, administrations of both parties (including the present one), have recognized with varying degrees of clarity that if a contemplated military operation would be sufficiently extensive in “nature, scope, and duration” to constitute a “war” within the meaning of Article I, § 8, cl. 11, congressional authorization would be required.
In this respect, presidential war powers are not exclusively a one-way ratchet. The Executive Branch does sometimes ratchet back prior expansive claims of inherent authority to use force in the absence of prior congressional authorization. Today, there can be little doubt that a conflict akin to the Korean police action in its nature, scope, and duration would amount to war in the constitutional sense and thus require congressional authorization. Indeed some recent administrations have implied as much in their treatment of the Korean precedent (see here at 8-9 and here at 331 n.5). And it should also be emphasized that even those uses of force not implicating the Declare War Clause, might still be prohibited as a matter of domestic law under Article 2(4) by virtue of the Take Care Clause.
Properly understood and situated in the context of subsequent Executive Branch legal positions, the Korean police action is a limited precedent, possibly neither as dangerous nor useful, as some may believe.
 There may be some doubt as to whether the Charter and relevant Security Council provisions required Truman to use force under the Take Care Clause given that the pertinent language of these instruments did not obligate states to use force.