In March 2016, shortly after the United States lifted sanctions on Iran over its nuclear program, then–Treasury Secretary Jack Lew gave a speech reflecting on the lessons Barack Obama’s administration had learned. Sanctions, he said, had “become a powerful force in service of clear and coordinated foreign policy objectives,” but the United States should be sure to use them “only to address significant threats to national security.” Overusing them, he warned, could dull their effectiveness. His logic was simple: Sanctions work because they cut targets off from dealing with U.S. citizens and American financial institutions—a complete severance from the world’s largest economy and its most important financial center. If Washington used this power idly, Lew suggested, it could encourage countries to find partners outside of the United States, and undermine sanctions’ deterrent effect.
Both the executive and legislative branches seem to have ignored Lew. Since his speech, the United States has reimposed sweeping sanctions on Iran, with restrictions on currency transactions and the trading of airplane and automotive parts going into effect on August 6; expanded the penalties against Russia and Venezuela; and pursued a maximum economic-pressure campaign against North Korea. Just after Donald Trump’s controversial Helsinki summit with Russia’s President Vladimir Putin, a bipartisan group of senators unveiled new legislation to tighten sanctions on Moscow. To punish Turkey for its detention of the American pastor Andrew Brunson, the administration imposed human-