DAWN E. JOHNSEN [*]
In February 1996, Congress presented President Bill Clinton with a dilemma. The National Defense Authorization Act for Fiscal Year 1996 included a provision requiring the armed forces to discharge individuals infected with the human immunodeficiency virus ("HIV"), including asymptomatic individuals.  President Clinton concluded that this provision "violate[d] equal protection by requiring the discharge of qualified service members living with HIV who are medically able to serve, without furthering any legitimate governmental purpose."  Yet the bill also appropriated $265 billion for military programs the President deemed "of great importance" to national security interests. 
President Clinton had vetoed an earlier version of the law due in part to the same HIV provision,  but decided against a second veto because of the military's need for the money appropriated by the bill.  President Clinton then faced the prospect of either enforcing the HIV provision, which in his view would both violate the constitutional rights of more than a thousand members of the armed forces and diminish military effectiveness, or disregarding the dictates of an act of Congress he had signed into law.
President Clinton's dilemma was far from novel. More than a century earlier, the House of Representatives impeached President Andrew Johnson because he claimed the authority to disregard a statute that he viewed as unconstitutional.  President Johnson fired the Secretary of War without first obtaining the consent of the Senate when consent arguably was required by the Tenure of Office Act,  which Congress had enacted over President Johnson's veto.  The Senate came within one vote of convicting and removing President Johnson from office for failing to enforce a law that the U.S. Supreme Court eventually agreed was unconstitutional.  A contemporary example: Congress continues to enact provisions that purport to allow a single house (or committee) of Congress to block executive branch action despite the Supreme Court's declaration that such "legislative vetoes" are unconstitutional.  Presidents routinely announce that they are not bound to comply with such provisions. 
This fundamental issue of the constitutional allocation of powers remains hotly contested. Constitutional commentators, as well as the political branches of our federal government, continue to debate the existence and parameters of the President's authority to refuse to enforce constitutionally objectionable statutes.  What should the President do if he believes enforcing a statute would violate the Constitution? In this article, I consider the legitimacy of what I will term "presidential non-enforcement,"  that is, whether and when the President may disobey an unambiguous congressional command enacted in conformity with the constitutionally prescribed lawmaking process on the ground that the President believes the law is unconstitutional.
Presidential non-enforcement in this narrow sense differs significantly from some other far more common executive branch responses to constitutionally objectionable statutes. Presidents often avoid constitutional problems, as they should, through their interpretation of ambiguous statutes or through the exercise of enforcement discretion.  These less controversial practices typically leave Congress free to consider the constitutional issue and enact more specific legislation if it disagrees with the President's views. Presidential non-enforcement, in the sense I will use the term, constitutes a more direct conflict with the core constitutional function of another branch of government. 
In Part II of this article, I review the two prevailing approaches to presidential non-enforcement found in the academic literature. Current views span the same constitutional spectrum as in the days of President Johnson's impeachment. …