This book represents a significant step forward in the study of subnational politics and democratization. Edward L. Gibson demonstrates how provincial officials maintain authoritarian regimes in democratic countries through their interactions with local populations and national and municipal leaders. Compared to other works, Boundary Control offers a fuller and more complete theory of strategies to sustain subnational authoritarianism. The book also emphasizes that “national democracy cannot escape an intimate association with subnational authoritarianism…. It empowers it and absorbs it into its legal and normative framework” (p. 172). This theoretical advance and real-world import make the book a must-read for those interested in democracy, regime change, or subnational politics.

The author's central argument is that authoritarian provinces can endure in democracies when their incumbents are able to keep conflict localized or, in Gibson's terms, exercise “boundary control.” Provincial leaders use three strategies to accomplish this. First, through “parochialization of power,” incumbents control local politics by establishing a dominant party. Second, incumbents achieve “nationalization of influence,” meaning that they sway national decisions that affect their provinces. They do this by securing national positions for themselves, ensuring that their supporters win national legislative seats, and delivering votes to the national ruling party. A final strategy used by incumbents is the “monopolization of national-subnational linkages.” Provincial leaders manipulate national funds sent to their territories, envoys who are assigned to monitor their activities, and institutions that are designed to coordinate provincial representation in the national capital.

The purpose of these strategies, in part, is to quash urban oppositions and mayors who might challenge provincial rule. For example, parochialization of power and monopolization of national-subnational linkages include efforts to weaken urban competitors through legislative malapportionment in order to favor rural areas and the control of national funds to municipalities.

Gibson takes his theory a step further by explaining how the “territorial regime” shapes the nature and success of these strategies. The territorial regime “governs the interactions among territorial units of the state … and specifies the division of powers between governments” within the state (p. 17). Greater centralization reduces provinces' autonomy to design their governments and thus forces provincial leaders to use informal, illegal means to execute the three strategies. Provincial regimes that rely on informal, illegal techniques are less stable because a democratic national government is more likely to challenge behavior that falls outside the law. Consequently, these provincial leaders must rely even more on the nationalization of influence in order to preserve their rule. A territorial regime that overrepresents particular types of provinces in national institutions can augment authoritarian enclaves' influence in the national capital. A final important characteristic of the territorial regime is whether it empowers or weakens municipalities. Empowered municipalities threaten provincial authoritarian regimes by facilitating the development of urban oppositions.

Four cases illustrate the strategies and territorial regimes' impact on them. Contemporary Mexico and the United States during Reconstruction are examples of high centralization, whereas contemporary Argentina and the United States following Reconstruction exhibit low centralization. Relative to the other cases, Mexico has symmetric representation of provinces in national institutions. Mexico also stands out because it has the most empowered municipalities, followed by the United States and then Argentina. Gibson considers evidence from each country in a separate chapter, preceded by a chapter that introduces the theory and another elaborating on it, and followed by a chapter that highlights the similarities and differences among the cases.

Gibson's explanation of the way in which subnational authoritarian regimes are created and maintained advances the field of study. Building upon other scholars' works—many of which, in turn, draw on a preliminary version of his argument published in 2005—the author offers the most comprehensive theory to date of subnational authoritarianism. Whereas most works examine relations only between provinces and the national government, Gibson includes municipalities and the strategies employed by provincial leaders to stem urban opposition. He also examines a wider array of tools than provincial leaders. Works by William Munro and Carlos Gervasoni, among others, focus on factors contributing to subnational authoritarianism, such as local electoral systems and distribution of federal funds. Gibson incorporates these influences and introduces numerous others in his framework of three strategies for maintaining subnational authoritarianism.

Where Gibson's theory is less complete is in explaining the democratization of subnational authoritarian regimes. According to the author, subnational authoritarianism begins to erode when local conflict is nationalized. He lays out the following scenario: A crisis occurs in a province, and local opposition brings it to the attention of outside actors and manages to link the local conflict to the outside actors' interests. The outside actors then devote resources to resolving the conflict and thus become involved in the struggle to rule the province. Gibson again draws on characteristics of the territorial regime, here to distinguish between the type of democratic transition—center-led and party-led. A center-led transition, whereby national authorities change provincial rules and institutions, is more likely in a decentralized country because provincial leaders use laws and institutions to maintain authoritarianism. A party-led transition, whereby a national party allies with the local opposition to win provincial offices, is more likely in centralized countries because provincial leaders use informal, illegal means to maintain authoritarianism.

Local opposition and national actors are essential to Gibson's argument about the demise of subnational authoritarian regimes: Local opposition attracts to the province national actors who dismantle authoritarianism. But it would be helpful to know under what conditions these actors can and do act. The book reveals that some, but not all, subnational authoritarian regimes in Argentina and Mexico have fallen. Can this be attributed to the presence or strength of local opposition? Gibson eschews the “intrinsic characteristics” of subnational territories in his explanation (p. 4), but features of a province and its regime can prevent the development of local oppositions and thus hinder democratization of a territory, as research by Maya Tudor and Adam Ziegfeld and my own work have shown. The rich empirical information in Boundary Control also shows that some national interventions in these countries have succeeded while others have failed (pp. 93–95, 127–33). What factors influence national actors' decisions to intervene and their likelihood of success if they do so? Gibson argues that a local opposition brings a crisis to national actors' attention and that they can more easily overturn subnational authoritarian regimes maintained through illegal, informal means. Work by Agustina Giraudy shows that numerous other factors increase the effectiveness of national interventions, as well as motivate them. Additional theorizing about the motivations and capacity of local oppositions and national actors would be helpful.

That said, Gibson's explanation of subnational democratization is an excellent beginning. Unlike other studies that have focused on the maintenance of subnational authoritarianism, this book also tackles change. Other scholars should use Gibson's ideas as a starting point, fleshing out the details about actors' motivations and capacities using existing and new research. More complete and thus even more valuable is his theory of the creation and maintenance of subnational authoritarian regimes. This theory advances our understanding of democracy and subnational politics and thus makes Boundary Control essential reading for many social scientists.