In an astounding display on the United States Senate floor Tuesday evening, Majority Leader Mitch McConnell effectively silenced Sen. Elizabeth Warren in the middle of her floor speech voicing opposition to attorney general nominee Sen. Jeff Sessions. McConnell interrupted Warren on procedural grounds saying that she had impugned Sen. Sessions during her speech and then effectively barred her from continuing. Warren, who was visibly miffed and then increasingly incredulous, was reading a letter from Coretta Scott King, wife of Martin Luther King Jr., submitted to the Senate in 1986 urging the body to block Sessions’ nomination as a federal court judge. The letter was addressed to none other than avowed segregationist Sen. Strom Thurmond, who was the chairman of the Judiciary Committee at the time.

“Mr. Sessions has used the awesome powers of his office in a shabby attempt to intimidate and frighten elderly black voters,” Warren read aloud from King’s letter. “For this reprehensible conduct, he should not be rewarded with a federal judgeship.” Moments later Sen. McConnell interrupted on the Senate floor. “The senator has impugned the motives and conduct of our colleague from Alabama,” McConnell. “I call the senator to order under the provisions of Rule 19.”

Rule 19 covers a whole host of procedural rules on debate etiquette on the Senate floor. In this case, the notable portion of the rule, is Section 2: “No Senator in debate shall, directly or indirectly, by any form of words impute to another Senator or to other Senators any conduct or motive unworthy or unbecoming a Senator.” Sen. Steve Daines, R-Mont., who was presiding in the chair, agreed with McConnell.

“I am surprised that the words of Coretta Scott King are not suitable for debate in the United States Senate,” Warren replied asking to be able to continue. Sen. McConnell objected, and Sen. Daines, repeating the words verbatim of a Republican staffer three feet in front of him, instructed Warren to take her seat. Warren appealed to the full Senate, but lost a party-line vote 49–43, which means, the Hill points out, that Warren “won’t be allowed to speak from the floor until after the Senate wraps up its debate on Sessions’ nomination, expected to occur on Wednesday evening.”