Research: Red Lines That Bind: International Law, Audience Costs, and Nuclear Counterproliferation in U.S. Foreign Policy

 In the summer of 2023, Stanford political science undergraduate Ethan Lee, BA '23, conducted research for his paper "Red Lines That Bind: International Law, Audience Costs, and Nuclear Counterproliferation in U.S. Foreign Policy," with support from the Iranian Studies Program, among other Stanford programs. 

"Amid escalating U.S.-Iran tensions in January 2020, President Donald Trump threatened to take military action against Iranian cultural sites in retaliation for Iran attacking Americans. Despite controversy over the international legality of the action, coupled with no retaliatory action in response to an Iranian missile strike against U.S. forces stationed in Iraq, Trump’s domestic political standing remained strong; indeed, his approval rating rose to a personal best of 49% at the end of the month. My thesis aimed to better understand this complex interplay between international law and domestic audience costs, i.e. the internal political costs that leaders incur for making and then backing down from foreign threats. More specifically, I examined whether and how the international lawfulness of coercive threats impacts the different components of domestic audience costs.

My thesis utilized an experimental survey to gauge a representative sample of the U.S. public’s reactions to a hypothetical foreign policy crisis between the U.S. and Iran. In the survey scenarios, Iran is on the brink of developing nuclear weapons. The U.S. President threatens to destroy all of Iran’s nuclear weapon facilities if it tests a nuclear weapon, with different treatment conditions’ scenarios varying on whether the military action is stated to be internationally lawful or unlawful, whether the President follows through or backs down from the threat once Iran tests a nuclear weapon, and—if they follow through—whether U.S. military action succeeded or failed.

My data revealed that the stated international legality of the threat, in conjunction with the President's subsequent actions, notably influenced levels of political support and perceived reputational damage. Notably, there was a “domestic audience benefit” when backing down from an internationally unlawful counterproliferation threat. Instead of paying political costs, a leader gains more political support from his domestic audience for backing down from an unlawful threat compared to not making a threat in the first place. There were no domestic audience costs for an internationally lawful counterproliferation threat. The magnitude and scale of the different components of domestic audience costs/benefits varied significantly based on international legality. Depending on the treatment, respondents’ individual-level characteristics and assumptions help explain their political support for the President.

The central finding of my research, that backing down from an internationally unlawful counterproliferation threat can result in a domestic audience benefit, is an intriguing twist to the prevailing domestic audience cost theory, which typically posits that leaders suffer political consequences for backing down from publicly communicated threats. While the concept of domestic audience benefits is intriguing, it suggests a degree of variability that warrants further exploration.

There is a need for additional experimental research to more robustly examine these effects, distinctly varying the context and treatment. These findings also raise questions concerning the impact of contradictory legal arguments on domestic audience costs. For the treatments that communicated the threat as internationally unlawful, my survey reassessed respondent approval of the President’s actions after being informed that the U.S. Department of State’s Legal Adviser argued that the attack was internationally lawful. This element was only included as a separate dependent variable, not incorporated into the treatments."