Although there is a tendency among contemporary political scientists to depreciate the importance or even the legitimacy of constitutional interpretation as a field of study, Amanda DiPaolo's Zones of Twilight shows us how much is lost if we ignore this type of inquiry. DiPaolo demonstrates how a very sophisticated analysis of constitutional theory can better elucidate the courts' recent decisions in cases relating to national security than any simple behavioral model. She explains that, “while the adjudication of the war powers have been an often discussed topic for analysis by scholars, the language of judicial decision making itself is not often a part of the analysis” (pp. 200–1). By paying attention to what judges say, she allows us to better understand what the courts are doing and how this may guide us in imposing effective limits on the exercise of national security powers. The book offers a unique and valuable perspective on the role of the courts in contemporary politics.

DiPaolo argues that “Americans have come to expect federal courts to declare actions by the government that are contrary to the Bill of Rights as unconstitutional … When a fundamental right, guaranteed by the Bill of Rights, is limited by government, courts typically apply the highest level of scrutiny” (pp. 2; 3). After all, she states, “there is only one Constitution and there is no suspension clause for emergency situations, an exception being the strict criteria imposed for suspending the writ of habeas corpus” (p. 206). Looking at actual war-powers cases, however, we see that the Supreme Court rarely uses “rights–based language in formulating its decisions” (p. 4). DiPaolo notes that this has led commentators such as Eric Posner and Adrian Vermeule to lament that “[w]hen emergencies strike, the executive acts, Congress acquiesces, and courts defer” (“Accommodating Emergencies,” in Mark Tushnet, ed., The Constitution in Wartime: Beyond Altruism and Complacency, 2005, p. 2).

DiPaolo, however, offers a more complex and more positive interpretation of judicial action. She claims that although the courts do not typically act in the name of the Bill of Rights, they do act in the name of statutory language and the separation of powers: “[T]he federal courts often decide war-powers cases based on statutory claims by looking at authority, or lack of, delegated to the president by Congress” (p. 2). The courts are often deferential to claims of government authority, but only “when the two elected branches of government are in agreement on the need to limit individual liberties” (p. 4). According to DiPaolo, this is consistent with the Founders' belief that “the Constitution's structure of government … would go on to protect liberties, when the Bill of Rights would not” (p. 6).

The author finds support for her argument in Justice Robert Jackson's famous concurring opinion in Youngstown Sheet and Tube v. Sawyer (343 US 579). Jackson makes a tripartite distinction among cases where 1) the president acts pursuant to an implied or expressed Congressional authorization, 2) the president acts in the absence of either a Congressional grant or denial of authority, or 3) the president acts in opposition to the expressed or implied will of Congress. In the first instance, the Court would exercise only the most minimal level of scrutiny and, in the second, the Court would use an intermediate level of scrutiny. In the third case, when the president acts in opposition to the express or implied will of Congress, the courts apply the strictest level of scrutiny. According to DiPaolo, Jackson's opinion “emphasizes a vision of shared powers. The president may have inherent power, but he wields it only with an endorsement from Congress” (p. 25).

DiPaolo admits that in practice, the Court often grants great deference to war-power claims on the part of the government, but she says that it is nonetheless a mistake to say that the courts simply defer to the president. Instead, she claims that “the courts actually defer to Congress, which in turn often defers to the executive” (p. 36). Such deference allows the political branches to make prudential decisions regarding political necessity in times of war, but it still leaves room for the courts to step in and place limits on such action when there is disagreement between the political branches.

DiPaolo tests her framework through the use of four case studies: military detentions, warrantless electronic surveillance, economic property rights, and, finally, free-speech cases. She concludes that in the first three instances, the courts do indeed rely almost exclusively on separation-of-powers language in articulating their decisions. In the fourth case, free speech, however, the courts use a rights-based language. Far from discrediting her argument about the courts' reliance on separation of powers, she contends that this exception demonstrates the problems inherent in a rights-based approach. Because such cases are decided in the context of war, the courts often allow latitude to Congress and the president in order to deal with the immediate substantive evils. The problem is that “the limits to the First Amendment allowed in times of war remain in times of peace” (p. 171). The constitutional exception to the First Amendment becomes a permanent legal precedent and thereby does lasting damage to our conception of constitutional rights.

The courts avoid this danger when they use the separation-of-powers framework as the basis of their decisions. Rather than establishing a constitutional rule, the courts have instead encouraged a constitutional dialogue among the three branches of government. The courts first look “for congressional authorization of executive actions. When seeing no authorization, the courts have suggested to the government to ask Congress for authorization” (p. 80). The courts defer to the political branches, but only when they are in agreement. When Congress opposes executive action, the courts will weigh in on the side of Congress. Thus, the prudential considerations of wartime necessity are taken account of through short-term political accommodation, rather than by a permanent modification of constitutional doctrine.

The major problem with DiPaolo's argument is that it assumes that separation-of-powers questions are primarily “political questions” and, moreover, that when faced with such questions, both the courts and the president should defer to Congress. Ironically, the author concludes that the judges' words in these cases serve mainly to defend their role as political actors. She never seriously considers the possibility that the Constitution defines distinctive types of power that provide judicially enforceable standards which the courts can use to judge the actions of both Congress and the presidency. When, for example, the Supreme Court claimed in Hamdi v. Rumsfeld that some procedural safeguards were necessary to protect the rights of detainees deemed to be enemy combatants, it was not merely deferring to Congress; it also was affirming its distinctive judicial role in protecting the due process rights of individuals against infringement by both the president and Congress. Under this more robust notion of the separation of powers, both the courts and the president are not merely restrained by the Constitution; they are also empowered by it. Neither the courts nor the president are dependent for their powers upon the statutory authorization of Congress.

In neglecting this alternative, DiPaolo is clearly in the mainstream of contemporary scholarship. What she does better than anyone else, however, is to clearly articulate this “Jacksonian” view of the separation of powers and trace its influence on war-powers cases from the American founding to today. This is a book worthy of serious engagement.