As we ponder the contemporary debate about the proper use of international and foreign law in interpreting U.S. constitutional law, it might be well to remember that in 1857, the Supreme Court, in its most infamous judgment, Dred Scott v. Sandford, was already struggling with the controversy. This Article looks first at the increasingly hostile position that international and foreign law took towards slavery in the period from the American Revolution to our Civil War. Second, we discuss the nine judicial opinions in Dred Scott and explain how the judges variously relied on international and foreign law to defend or attack slavery and to interpret the U.S. Constitution. The majority of that sharply divided Court, led by Chief Justice Taney, unhappily held that African Americans could never be U.S. citizens and that Congress could never make slavery illegal in the Western territories, the first time since Marbury v. Madison that the Supreme Court used judicial review to strike down an act of Congress. The Dred Scott judges disagreed, often emotionally, about whether the increasingly hostile attitude of international and foreign law towards slavery could or should affect outcomes in U.S. constitutional law. Third, and finally, we explore the lessons of Dred Scott. Most importantly, the case reminds us that American exceptionalism in international law and politics helped persuade some on the Supreme Court to protect our then so-called “peculiar institution,” slavery, and to disregard the progressive development of international and foreign law.