No U.S. president resorted to economic sanctions more often than did Donald Trump, whose administration issued about 3,800 new sanctions "designations" in a single term. There were many reasons for this, including Mr. Trump's penchant for targeting adversaries such as Iran, and for doing it unilaterally as opposed to waiting for cooperation with allies. In a broad sense, though, he was just accelerating a trend that began with his predecessors, including President Barack Obama, who made 2,350 new designations in his second term (though he "delisted" targeted countries, individuals and entities more often than Mr. Trump did). As of Oct. 1, 2021, there were 9,421 sanctions designations in effect, according to the Treasury Department, which is responsible for enforcing them. That's a tenfold increase since the terrorist attacks of Sept. 11, 2001, spawned a new era in the use of sanctions, aimed at defunding far-flung terrorist networks and other nonstate networks as well as traditional state adversaries. In addition to counterterrorism, the goals include fighting nuclear proliferation by Iran and North Korea; punishing human rights violations or corruption; and battling cybercrime. And it's easy to see why the United States resorts so often to sanctions: They promise the achievement of foreign policy goals without the use of armed force, by taking advantage of the United States' pivotal role in global finance and trade. The question, though, is whether sanctions are yielding diminishing returns. Then-Treasury Secretary Jack Lew raised that issue in one of his last official speeches — five years ago. In the same spirit, the current secretary, Janet L. Yellen, promised the Senate at her confirmation hearing that she would conduct a review of all existing sanctions. Some risks — that a given sanction will simply fail to achieve its goals or will create unfair difficulties for U.S. businesses and humanitarian aid organizations — are familiar. The administration has already taken steps to mitigate this by issuing humanitarian relief licenses for Syria, Venezuela and Iran for covid-related aid, and a more general one for Afghanistan. More novel is concern that the heavy U.S. use of so-called secondary sanctions, which not only ban dealings with certain individuals, companies or governments but also stop third parties from dealing with them, may alienate even friendly countries. In a worst-case scenario, the United States would cause countries to find cryptocurrency alternatives to the U.S. dollar and U.S.-dominated financial transactions systems.