with the power to interpret the nature and extent of individual citizens' obligations. Lomasky concludes that constitutional government might be better understood in terms of covenant than in terms of social contract. 
In "Constitutionalism in the Age of Terror," Michael Zuckert and Felix Valenzuela argue that constitutions have two primary aims that may sometimes come into conflict with each other. On the one hand, a constitution must limit and control the power of government so that it does not harm the citizens who live under its rule. On the other hand, a constitution must ensure that the government has sufficient power to achieve the common good and to safeguard its citizens against aggression. The tension between these two aims becomes especially apparent in emergency situations (e.g., when government must confront the threat of terrorism). In such situations, it is tempting to say that limits on governmental power (especially limits on the power of the executive branch) must be set aside so that the government may quickly and effectively respond to the threat at hand. Zuckert and Valenzuela examine four models for understanding how a constitution should channel and control governmental power in situations of emergency. The Whig model (which takes its name from the seventeenth-century English political party) maintains that there must be strict limits on governmental power, and especially on executive power, even in emergencies. The Jeffersonian model rejects the inclusion of emergency powers within the constitution, but acknowledges that it may sometimes be necessary for the executive to act outside the bounds of the constitution in extraordinary situations. The Hamiltonian model maintains that the powers required to confront extraordinary circumstances should be contained within the constitution itself, and looks to the executive to exercise these powers. The Madisonian model agrees that extraordinary powers should be provided for within the constitution, but holds that these powers should be vested in the legislature rather than in the executive. Zuckert and Valenzuela discuss each of these models in detail, relating them to contemporary debates over the limits of governmental power in the context of the war on terror. They conclude that the Madisonian model does the best job of limiting government while at the same time giving it the power it needs to confront the dangers of the modern world. 
The collection continues with three essays that focus on specific parts or provisions of a constitution. In "The Liberal Constitution and Foreign Affairs," Fernando R. Tesón attempts to outline the foreign relations clauses that should ideally be included in the constitution of a liberal society. On his view, an ideal constitution should enable the government to implement a morally defensible foreign policy, which implies a commitment to the defense of human liberty and prosperity. A government defends liberty by protecting its citizens and its territory from aggression, but also by protecting its liberal institutions against outside forces that would attempt to undermine them. A commitment to liberty also implies that a liberal government should promote the advancement of freedom around the globe-when this is possible and when the cost is not prohibitive. At the very least, a liberal government should seek to ally itself with other like-minded governments and should refrain from cooperating with tyrannical regimes. Moreover, a liberal government should promote prosperity by fostering free trade at home and abroad. Tesón goes on to apply these general principles to the design of a liberal constitution. He argues that a constitution's war-power provisions should be designed to secure combat-readiness and to allow for a flexible executive who will be able to respond to threats readily and effectively. At the same time, Tesón recommends that the legislative branch should have a role in authorizing all large-scale uses of military force. In terms of promoting free trade, he argues that the government should be prohibited from adopting protectionis