In a speech on the Senate floor Monday announcing his opposition to the confirmation of Judge Ketanji Brown Jackson to the Supreme Court, Sen. Tom Cotton (R-Ark.) pointed to the judge’s past work as a federal public defender, which included defending Guantánamo detainees. To make his point, he brought up another Jackson: Supreme Court Justice Robert H. Jackson, who served on the court from 1941 until his death in 1954.

“You know, the last Judge Jackson left the Supreme Court to go to Nuremberg to prosecute the case against the Nazis,” he said. “This Judge Jackson might have gone there to defend them.”

It’s true the justice left the court temporarily to prosecute Nazis at Nuremberg after World War II. But here’s the thing: Jackson not only supported the Nuremberg defendants’ right to counsel, he was a key part of the governing body that enshrined it into international law.

On May 2, 1945, President Harry S. Truman appointed Jackson to lead an American delegation to prepare and prosecute war crimes charges against European Axis powers. The appointment of such a high-ranking official prompted the other Allied powers to take the trials seriously, according to St. John’s University law professor and Jackson scholar John Q. Barrett.

But before trials could even start, the international delegation had to agree on a framework. There was not yet an International Criminal Court, and the crimes had taken place in many different countries. All that summer of 1945, Jackson worked in London with his British, French and Soviet counterparts on what became known as the London Charter, establishing the rules of the International Military Tribunal. He signed it on behalf of the United States on Aug. 8, 1945.

“The constitution of the Nuremberg trials was a constitution [Jackson] wrote,” Barrett told The Washington Post. “He believed in it seriously.”

Section Four, Article 16 concerned safeguards for a fair trial, including that a “Defendant shall have the right to conduct his own defense before the Tribunal or to have the assistance of Counsel.”