Washington DC - Does Donald Trump have the right to call prosecutors "fascist thugs," or advise those testifying against him to keep quiet?

Those are the questions a federal appeals court in Washington will hear Monday as the ex-president's lawyers contest a gag order imposed on him during one of Trump's criminal trials related to the 2020 election.

The gag order – a set of restrictions on what Trump is allowed to say publicly about a given set of legal proceedings – was imposed by Judge Tanya Chutkan, overseeing the federal case against him for allegedly trying to overturn the 2020 election.

She has restricted statements that "target" prosecutors, court personnel, and witnesses, which prosecutors argue could endanger people involved in the trial.

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But the gag order, currently temporarily lifted during Trump's appeal, will run up against First Amendment protections guaranteeing free speech.

The country's premier civil liberties group – hardly a Trump ally, historically – has criticized the gag order.

"The entire order hinges on the meaning of the word 'target,'" the American Civil Liberties Union has written. "But that meaning is ambiguous."

Chutkan did, while imposing the gag order, recognize Trump's right to criticize his White House successor, Joe Biden, whom the Republican frontrunner will likely face in next year's presidential election, given current polling.

But Trump's lawyers have argued that the restrictions on him in the trial, set to start in March, will have an undue influence on his 2024 campaign. The Iowa Republican Caucus is set for January.

"The Gag Order installs a single federal judge as a barrier between the leading candidate for President, President Donald J. Trump, and every American across the country," his lawyers wrote.

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To clarify the restrictions on Trump, Chutkan cited a post that Trump made on his Truth Social website questioning whether his former chief of staff Mark Meadows took an immunity deal to testify against him, saying only "weaklings and cowards" would do so.

The judge said that sort of speech should be restricted.

Prosecutors argue that some of Trump's statements about his trial "consist of ad hominem attacks using inflammatory language likely to arouse angry or violent feelings in the listener, rather than reasoned argument."

"These are precisely the sorts of statements that pose a substantial likelihood of material prejudice to the proceedings," they said, arguing that the gag order is clear on what is and isn't allowed.

Trump has a "pattern," they argue, "stretching back years, in which people publicly targeted by the defendant are... subject to harassment, threats and intimidation."

Catherine Ross, a professor at the George Washington University Law School, told CNN she doubted Trump's appeal would succeed in rescinding the gag order.

"It is a foundational principle that First Amendment rights to speak may sometimes have to give way to the integrity of the judicial process and the importance of guaranteeing a fair trial," she said. "This is a routine kind of limitation on criminal defendants."

Trump's lawyers have argued that an alternative to the gag order could be to delay the trial until 2025 – after next year's election.

But prosecutors say that will simply reward Trump for his "egregious" statements.