The Joint Comprehensive Plan of Action (JCPOA) was the product of aggressive “secondary sanctions”—innovative sanctions that put economic pressure on the target state by punishing states and entities that engage in transactions with the target state. Prior to the JCPOA, the United States used secondary sanctions to “outcast” Iran—isolate it from the international community. After Iran entered into the JCPOA, these sanctions were removed as a reward for its cooperation. In May 2018, however, the United States withdrew from the JCPOA and re-imposed the secondary sanctions in order to “re-outcast” Iran. But unlike the pre-JCPOA outcasting regime, the re-outcasting regime was not imposed in response to any violation of international law by Iran; instead, it was imposed for solely policy reasons. As a result, members of the international community condemned the use of secondary sanctions as politically motivated and illegitimate. Although the use of secondary sanctions is a relatively new phenomenon, it has become increasingly more prevalent since the Iran sanctions regime, serving as one of the main sources of pressure against nations such as Cuba, North Korea, Russia, and Venezuela. In contrast to the growing prominence of secondary sanctions, however, the academic literature on the topic remains thin. This piece seeks to fill that gap. By comparing the pre-JCPOA outcasting regime with the re-outcasting regime, this piece provides a timely insight into the counter-productive consequences of imposing secondary sanctions for purely policy reasons. This piece highlights that without international law, secondary sanctions are viewed as illegitimate, which leads to defiance by states and creates a “chilling effect” that makes cooperation less attractive for the outcast. Thus, this piece proposes that the United States should only impose secondary sanctions in response to a state’s violation of international law in order to avoid undermining the power of these sanctions in the long run. [ABSTRACT FROM AUTHOR]