“I am surprised that the words of Coretta Scott King are not suitable for debate in the United States Senate,” Warren complained Tuesday. Her phrasing was imprecise: It wasn’t that the words were unsuitable per se. Warren, a Massachusetts Democrat, was reading from a letter that the widow of Martin Luther King Jr. wrote at the time of Sessions’s nomination, opposing it. King laid out a devastating broadside, over the course of 10 pages, arguing he was unfit for the bench, and that his confirmation would undo her husband’s work. Coretta Scott King concluded:

I do not believe Jefferson Sessions possesses the requisite judgment, competence, and sensitivity to the rights guaranteed by the federal civil rights laws to qualify for appointment to the federal district court. Based on his record, I believe his confirmation would have a devastating effect on not only the judicial system in Alabama, but also on the progress we have made everywhere toward fulfilling my husband's dream that he envisioned over twenty years ago. I therefore urge the Senate Judiciary Committee to deny his confirmation.

Senator Strom Thurmond, the infamous former segregationist from South Carolina who chaired the Judiciary Committee did not enter the letter into the congressional record, meaning it was for a time lost, until The Washington Post’s Wesley Lowery resurfaced it earlier this year.

The letter was a central part of the successful effort to defeat Sessions’s nomination. The Judiciary Committee voted against recommending his nomination to the broader Senate, then deadlocked on whether to send the nomination on without a recommendation, effectively killing it. One pivotal vote was Alabama Senator Howell Heflin, a Democrat, who began as a Sessions supporter but changed his mind over the course of the testimony. Sessions’s nomination was withdrawn, even though Republicans, the party of President Reagan, held a majority that was one seat larger than the GOP’s edge today.

Warren read from the same letter from King on Tuesday, as well as another from the late Senator Edward Kennedy, who had called Sessions a “disgrace to the Justice Department,” when she was ruled to have breached decorum. McConnell charged that Warren had “impugned the motives and conduct of our colleague from Alabama.” Put differently, the very words that helped to mortally wound Sessions’s nomination 30 years ago, when he was merely a United States attorney had become anathema when Sessions joined the Senate in 1997—replacing Heflin, the man who had voted against him.

Like many ancient customs, the rule enforced against Warren was born out of a genuine concern: The prohibition against impugning a colleague was installed after Senator John McLaurin and Ben Tillman of South Carolina got into a fistfight on the floor in 1902. But like many century-old rules, this one produces peculiar results when applied today, such as the notion that King’s words, acceptable in 1986, are not acceptable now that Sessions is a member of the club.