Poplin is a Law Clerk at the United States Court of Appeals for the Eighth Circuit in the Chambers of Honorable Raymond Gruender in St. Louis. He graduated from Yale University Law School in 2019 where he focused on national security law. At Yale, he was the Executive Editor of the Yale Law Journal and host of the Yale Law Journal Podcast. He was also a student contributor to Lawfare and a research assistant to Jack Goldsmith, for whom he worked on treaty issues and cyber policy, and Paul Gewirtz for whom he conducted research on U.S.-China relations, including traveling to China for meetings/research. He completed his first year at Harvard Law School where he was Vice-President of the Harvard National Security Law Society and Senior Editor on the Harvard National Security Journal. During summer 2017 he was a legal intern in the Office of General Counsel at the Department of Defense. He was previously a Research Assistant in Governance Studies at the Brookings Institution and an Associate Editor of the Lawfare blog. He provided research assistance on projects related to U.S. national security policy and law related to detention and Guantanamo, the U.S. targeted killing program, NSA surveillance, and cyber security. In addition to assisting Senior Fellow Benjamin Wittes, he wrote his own research projects on Lawfare and edited manuscripts and posts.