Former president Donald Trump’s claim that the First Amendment shields his conduct leading up to the Jan. 6 Capitol riot is legally “spurious” and should be rejected as a federal court considers lawsuits that allege he incited the violence, four prominent First Amendment lawyers and scholars argued Thursday.

Targeting a key defense raised by lawyers for Trump and co-defendants including Rudolph W. Giuliani and Rep. Mo Brooks (R-Ala.), the legal experts said that courts have long recognized that speech central to a crime — such as the political intimidation of voters, lawmakers and government officials — is barred and not protected by the Constitution.

In a 23-page proposed friend-of-the-court brief filed Thursday in a case brought by members of Congress and Capitol police, the legal scholars argued that courts must strike a balance between protecting freedom of political speech and preventing political intimidation.

“Granting constitutional protection to the statutorily proscribed acts of political intimidation in the guise of ‘speech’ would render the government incapable of carrying out its functions, including its core democratic function of protecting the ability of all eligible citizens to engage freely and without coercion in the democratic process, whether by voting or by supporting and advocating for candidates,” the scholars wrote.

The four signers were First Amendment lawyer Floyd Abrams, who has fought several precedent-making cases in court, Berkeley law school dean Erwin Chemerinsky, former Harvard Law School dean Martha Minow and noted constitutional scholar Laurence Tribe.

“The movants believe that it is important not only to reject plaintiffs’ spurious and thinly developed First Amendment defenses, but to do so on grounds that preserve the effectiveness of political-intimidation statutes generally,” they added.

Trump attorney Jesse Binnall has asked U.S. District Judge Amit P. Mehta of Washington to toss out cases filed by Reps. Bennie G. Thompson (D-Miss.), Eric Swalwell (D-Calif.) and injured U.S. Capitol Police officers seeking damages, citing the president’s “absolute immunity” from the civil suit on separation-of-powers and free speech grounds.

Binnall wrote that Trump’s claims of election fraud and theft were rooted in opposing Congress’s vote on Jan. 6 to confirm the results of the 2020 election.

“It is well recognized that rousing and controversial speeches are a key function of the presidency,” Binnall argued. “That is especially true when, as is the case here, the President is advocating for or against congressional action.”

The plaintiffs assert that Trump’s baseless and incendiary statements were part of a conspiracy with co-defendants such as extremist members of groups such as the Oath Keepers and Proud Boys. They are accused of egging on the riot along with other speakers including Brooks, Giuliani and Donald Trump Jr. at a fiery rally that morning at the White House Ellipse.

At the rally, the then-president urged attendees to “fight like hell” and march to the Capitol, “whipping them into a frenzy and turning them into a violent mob that participated in the attack,” Swalwell claimed.

The Capitol breach forced the evacuation of lawmakers, contributed to five deaths and led to assaults on nearly 140 police officers, authorities say.

Swalwell, a former House impeachment manager, argued the Trump speakers “all conspired with … each other, and others to subvert the will of the people in the 2020 election.” Swalwell’s suit said the defendants violated the Reconstruction-era Ku Klux Klan Act, which was passed to prohibit violent interference in Congress’s constitutional duties such as the Klan’s reign of terror to disenfranchise Black citizens and White supporters after the Civil War.

Now part of a civil rights statute known as “Section 1985,” the law authorizes lawsuits against people who conspire to interfere with government, obstruct justice or deprive others of equal protection under the law, such as by threatening voters, candidates, or the courts.

The First Amendment scholars noted in their brief that courts historically have defended inflammatory political speech absent evidence that it incited imminent lawless action, or that a speaker seriously intended a “true threat” of violence — lines they argue Trump’s statements almost certainly crossed.

However, relying on such grounds could result in weakening First Amendment protections, while simultaneously “devastating” enforcement if courts interpret political intimidation laws as requiring proof of perpetrators’ intent, they wrote. Rather than apply those First Amendment tests with potentially harmful and unintended consequences to democracy, it would be better to shore up political-intimidation laws, they said, since many modern forms of intimidation do not involve threats of imminent violence but coercion of voters and elections officials.

“Although the January 6 insurrection may be the most spectacular example of incitement and ‘true threat’ in American history, modern political intimidation often takes subtler forms …,” the constitutional scholars wrote, such as “aggressive poll-watching, anonymous threats of harm, frivolous and excessive voter registration challenges, and coercion by employers,” as well as baseless threats of legal harm.

Carving out a “categorical” exception from the First Amendment for speech integral to political intimidation, they concluded, “also will preserve the efficacy of the political-intimidation statutes on which the health of our democracy depends.”

Before Trump’s impeachment acquittal in February, three of the four who wrote the amicus brief signed on to letters joined by more than 100 constitutional scholars earlier this year agreeing that the First Amendment did not prevent the Senate from convicting and disqualifying him from holding future office.

In a separate filing, lawyers for Swalwell raised similar arguments, warning that Trump’s legal interpretation would weaken civil rights laws “beyond recognition,” adding that the former president was not “petitioning the government for redress,” but “unleash[ing] a violent mob at the Capitol to prevent Congress from carrying out its constitutional duties.”

Trump and others conspired “through a months-long campaign of lies and deceit that culminated in violence-laced calls to save a country they claimed was being stolen,” knowing the propensity of some listeners to engage in violence, that Trump approved of such violence and had pressured election officials and Vice President Mike Pence to overturn the results, attorneys wrote.

They concluded, “And when hordes of Trump’s supporters did just that, Donald Trump reportedly was happy with the result.”