Executive orders are one vehicle of many through which the President may exercise his authority. While the President's ability to use executive orders as a means of implementing presidential power has been established as a matter of law and practice, it is equally well established that the substance of an executive order, including any requirements or prohibitions, may have the force and effect of law only if the presidential action is based on power vested in the President by the U.S. Constitution or delegated to the President by Congress. The President's authority to issue executive orders does not include a grant of power to implement policy decisions that are not otherwise authorized by law. Indeed, an executive order that implements a policy in direct contradiction to the law will be without legal effect unless the order can be justified as an exercise of the President's exclusive and independent constitutional authority. This report first reviews the "definition" of an executive order and how it is distinguishable from other written instruments, and then provides an overview of the President's constitutional authority to issue such directives. Next, the report discusses the legal framework relied on by the courts to analyze the validity of presidential actions, and also discusses the roles of the President and Congress in modifying and revoking executive orders. Presidents have historically utilized various written instruments to direct the executive branch and implement policy. These include executive orders, presidential memoranda, and presidential proclamations. The definitions of these instruments, including the differences between them, are not easily discernible, as the U.S. Constitution does not contain any provision referring to these terms or the manner in which the President may communicate directives to the executive branch. A widely accepted description of executive orders and proclamations comes from a report issued in 1957 by the House Government Operations Committee: Executive orders and proclamations are directives or actions by the President. When they are founded on the authority of the President derived from the Constitution or statute, they may have the force and effect of law.... In the narrower sense Executive orders and proclamations are written documents denominated as such.... Executive orders are generally directed to, and govern actions by, Government officials and agencies. They usually affect private individuals only indirectly. Proclamations in most instances affect primarily the activities of private individuals. Since the President has no power or authority over individual citizens and their rights except where he is granted such power and authority by a provision in the Constitution or by statute, the President's proclamations are not legally binding and are at best hortatory unless based on such grants of authority. The distinction between these instruments—executive orders, presidential memoranda, and proclamations—seems to be more a matter of form than of substance, given that all three may be employed to direct and govern the actions of government officials and agencies. Moreover, if issued under a legitimate claim of authority and made public, a presidential directive could have the force and effect of law, "of which all courts are bound to take notice, and to which all courts are bound to give effect." The only technical difference is that executive orders and proclamations must be published in the Federal Register , while presidential memoranda are published only when the President determines that they have "general applicability and legal effect." Just as there is no definition of executive orders, presidential memoranda, and proclamations in the U.S. Constitution, there is, likewise, no specific provision authorizing their issuance. As such, authority for the execution and implementation of these written instruments stems from implied constitutional and statutory authority. In the constitutional context, presidential power is derived from Article II of the U.S. Constitution, which states that "the executive power shall be vested in a President of the United States," that "the President shall be Commander in Chief of the Army and Navy of the United States," and that the President "shall take Care that the Laws be faithfully executed." The President's power to issue these directives may also derive from express or implied statutory authority. Despite the amorphous nature of the authority to issue executive orders, presidential memoranda, and proclamations, these instruments have been employed by every President since the inception of the Republic. Notably, executive orders historically have been more contentious as Presidents have issued them over a wide range of controversial areas such as the establishment of internment camps during World War II; the suspension of the writ of habeas corpus; and equal treatment in the armed services without regard to race, color, religion, or national origin. However, Presidents have also used executive orders for arguably more mundane governing tasks such as directing federal agencies to evaluate their ability to streamline customer service delivery and establishing advisory committees. Because there is no underlying constitutional or statutory authority that dictates the circumstances under which the President must issue an executive order, it is probable that the President also could have chosen to issue presidential memoranda rather than executive orders. As a matter or historical practice, however, it seems that Presidents are more apt to utilize executive orders on matters that may benefit from public awareness or be subject to heightened scrutiny. Memoranda, on the other hand, are often used to carry out routine executive decisions and determinations, or to direct agencies to perform duties consistent with the law or implement laws that are presidential priorities. Presidents' broad usage of executive orders to effectuate policy goals has led some Members of Congress and various legal commentators to suggest that many such orders constitute unilateral executive lawmaking that impacts the interests of private citizens and encroaches upon congressional power. The Supreme Court in Youngstown Sheet & Tube Co. v. Sawyer established the framework for analyzing whether the President's issuance of an executive order is a valid presidential action. As discussed below, the framework established by Justice Robert H. Jackson in his concurring opinion has become more influential than the majority opinion authored by Justice Hugo Black, and has since been employed by the courts to analyze the validity of controversial presidential actions. In 1952, President Harry S. Truman, in an effort to avert the effects of a workers' strike during the Korean War, issued an executive order directing the Secretary of Commerce to take possession of most of the nation's steel mills to ensure continued production. This order, challenged by the steel companies, was declared unconstitutional by the Supreme Court in Youngstown . Justice Black, writing for the majority, stated that under the Constitution, "the President's power to see that laws are faithfully executed refuted the idea that he is to be a lawmaker." Specifically, Justice Black maintained that presidential authority to issue such an executive order, "if any, must stem either from an act of Congress or from the Constitution itself." Applying this reasoning, the Court concluded the President's executive order was effectively a legislative act because no statute or constitutional provision authorized such presidential action. The Court further noted that Congress rejected seizure as a means of settling labor disputes during consideration of the Taft-Hartley Act of 1947, and instead adopted other processes. Given this characterization, the Court deemed the executive order to be an unconstitutional violation of the separation-of-powers doctrine, explaining that "the Founders of this Nation entrusted the lawmaking power to the Congress alone in both good and bad times." While Justice Black's majority opinion in Youngstown seems to refute the notion that the President possesses implied constitutional powers, it is important to note that there were five concurrences in the decision, four of which maintained that implied presidential authority adheres in certain contexts. Of these concurrences, Justice Jackson's has proven to be the most influential, even surpassing the impact of Justice Black's majority opinion. Jackson's concurrence, as discussed below, is based on the proposition that presidential powers may be influenced by congressional action. In his concurring opinion, Justice Jackson established a tripartite scheme for analyzing the validity of presidential actions in relation to constitutional and congressional authority. Because "[p]residential powers are not fixed but fluctuate, depending upon their disjunction or conjunction with those of Congress," Justice Jackson acknowledged that the three categories he established were a "somewhat over-simplified grouping," but they nonetheless assist in identifying "practical situations in which a President may doubt, or others may challenge, his powers, and by distinguishing roughly the legal consequences of this factor of relativity." Under the tripartite scheme, the President's authority to act is considered at a maximum when he acts pursuant to an express or implied authorization of Congress because this includes "all that he possesses in his own right plus all that Congress can delegate." Such action "would be supported by the strongest of presumptions and the widest latitude of judicial interpretation." However, where Congress has neither granted nor denied authority to the President, Justice Jackson maintained that the President could still act upon his own independent powers. For this second category, there is a "zone of twilight in which [the President] and Congress may have concurrent authority, or in which distribution is uncertain." Under these circumstances, Justice Jackson observed that congressional acquiescence or silence "may sometimes, at least as a practical matter, enable, if not invite, measures on independent presidential responsibility," yet "any actual test of power is likely to depend on the imperatives of events and contemporary imponderables rather than on abstract theories of law." In contrast, the President's authority is considered at its "lowest ebb" when he "takes measures incompatible with the express or implied will of Congress ... for he can only rely upon his own constitutional powers minus any constitutional powers of Congress over the matter." Justice Jackson observed that courts generally "sustain exclusive presidential control ... only by disabling the Congress from acting upon the subject." He cautioned that examination of presidential action under this third category deserved more scrutiny because for the President to exercise such "conclusive and preclusive" power would endanger "the equilibrium established by our constitutional system." Applying this framework to President Truman's action, Justice Jackson determined that analysis under the first category was inappropriate, due to the fact that seizure of the steel mills had not been authorized by Congress, either implicitly or explicitly.