In the summer of 1964, not long after President Lyndon B. Johnson signed the landmark Civil Rights Act, a Ku Klux Klan member named Clarence Brandenburg invited a TV news reporter to a rally near Cincinnati.

Brandenburg, a television repairman, was wearing a hood, as were a dozen other Klan members who gathered. Some had guns. They burned a cross while spewing racist and antisemitic commentary. Brandenburg also made a threat about seeking vengeance.

“We’re not a revengent organization,” he said, inventing a new word. “But if our president, our Congress, our Supreme Court continues to suppress the White, Caucasian race, it’s possible that there might have to be some revengence taken.”

What happened next has shaped First Amendment law for more than 50 years, laying down a legal doctrine at the center of former president Donald Trump’s Senate impeachment trial.

Brandenburg was arrested under an Ohio law that prohibited advocating violence to force political change. After being convicted and sentenced to a year in jail, he sued, alleging his free speech rights had been violated.

The case made it all the way to the Supreme Court, which ruled in the Klan member’s favor in 1969 and established a test to determine whether speech such as Brandenburg’s could be prohibited. Speech that is “directed at inciting or producing imminent lawless action” or “likely to incite or produce such action” was not protected by the First Amendment, the court said.

Though Trump’s impeachment is not a criminal trial, his lawyers in their legal briefs referenced Brandenburg v. Ohio, arguing that Trump didn’t direct his supporters to attack the Capitol. House managers prosecuting the case took the opposite view on Brandenburg and Trump, saying he crossed the line set up by the Supreme Court.

On Wednesday, the second day of the impeachment trial, Rep. Jamie B. Raskin (D-Md.), the lead House manager, called Trump the “inciter in chief” and argued that the ex-president had “no credible” First Amendment defense for urging the mob to attack the Capitol.

Then, on Friday, Trump attorney David Schoen invoked Brandenburg in accusing House managers of selectively editing video of Trump’s Jan. 6 speech to make it seem like the president was inciting the crowd.

Constitutional-law scholars have been debating the issue for weeks in dueling op-eds.

Richard A. Wilson, a University of Connecticut law professor and co-author of a recent journal article about incitement in the age of populism, said the revival of the Klan case is a broader reminder of how free speech was extremely limited until the civil rights movement.

“We like to tell ourselves as Americans we’ve had all these great First Amendment rights for the entire period of our republic, but it’s simply not true,” Wilson said. “We were very repressive of speech until the end of the 1960s, and it was civil rights that opened the door.”

And that meant protecting speech that many would deem deplorable, including Brandenburg’s.

In his speech at the Klan rally, Brandenburg — using words too ugly to publish then or now — demanded that Black people be deported to Africa and Jews to Israel.

He is lucky his wish didn’t come true.

Brandenburg’s legal team from the American Civil Liberties Union included Allen Brown, a Jewish man, and Eleanor Holmes Norton, an African American woman.

Norton, now 83, is the District’s longtime delegate in Congress.

“I certainly disagreed with everything he said,” Norton said in an interview. “He called African Americans all kinds of pejorative names, terrible things. But for me, it was an easy case. It’s just the kind of case that you should look at to test whether you are for free speech or not.”

Told that Trump’s lawyers had referenced Brandenburg v. Ohio in their legal briefs, Norton said, “I don’t blame them.”

But she thinks Trump’s actions differ from Brandenburg’s. The Klan leader’s speech, Norton said, did not seem aimed at “imminent lawless action,” as the Supreme Court’s test required. She thinks Trump did cross that line.

“His lawyers need to defend him with speech because there’s no other way to defend it,” she said.

It’s unclear what became of Brandenburg, who died in 1986. News reports indicate he was arrested years after his Supreme Court win for harassing a Jewish neighbor.

But Norton remembers how thankful Brandenburg was for the Jewish and African American lawyers who defended his right to free speech, ugly or not.

“He was so appreciative of the argument that had been made,” Norton said. “I guess he forgot his racism for a moment.”

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