How powerful are presidents in exercising their unilateral authorities? For the past several decades, both academic researchers and political observers have noted the importance of executive directives such as executive orders to a president's policy agenda and have sought to understand the underlying processes that define these presidential decisions. Yet one puzzle remains, especially in relation to executive unilateral authority: why are there “instances where the chief executive can brandish unilateral action as a weapon,” and yet “there are other times where the President comes across as extremely sensitive to the preferences of those in the majority in Congress the legislative parties to which they belong” (p. 178). Along with another recently published book on the unilateral presidency, Michelle Belco and Brandon Rottinghaus's The Dual Executive: Unilateral Orders in a Separated System, Fang-Yi Chiou and Lawrence S. Rothenberg's attempt to address what they called the “enigma of presidential power” represents some of the latest thinking on the nature of presidential power generally and the determinants of unilateral actions specifically.

Most impressively, Chiou and Rothenberg combine formal theoretical modeling with rigorous empirical methods to tackle a particular thorny question that has eluded