In Reagan's Gun-Toting Nuns, Theresa Keeley analyzes the role of intra-Catholic conflict within the framework of U.S. foreign policy formulation and execution during the Reagan administration. She challenges the preponderance of scholarship on the administration that stresses the influence of evangelical Protestants on foreign policy toward Latin America. Especially in the case of U.S. engagement in El Salvador and Nicaragua, Keeley argues, the bitter debate between U.S. and Central American Catholics over the direction of the Catholic Church shaped President Reagan's foreign policy.

The flash point for these intra-Catholic disputes was the December 1980 political murder of four American Catholic missionaries in El Salvador. Liberal Catholics described nuns and priests in Central America who worked to combat structural inequality as human rights advocates living out the Gospel's spirit. Conservative Catholics saw them as agents of class conflict who furthered the so-called Gospel according to Karl Marx. The debate was an old one among Catholics, but, as Reagan's Gun-Toting Nuns contends, it intensified as conservative, anticommunist Catholics played instrumental roles in crafting U.S. policy to fund the Salvadoran government and the Nicaraguan Contras.

Reagan's Gun-Toting Nuns describes the religious actors as human rights advocates and, against prevailing understandings of the fundamentally secular activism related to human rights, highlights religion-inspired activism during the Cold War. In charting the rightward development of American Catholicism, Keeley provides a new chapter in the history of U.S. diplomacy and shows how domestic issues such as contraception and abortion joined with foreign policy matters to shift Catholic laity toward Republican principles at home and abroad.