Last month saw the judge presiding over former President Donald Trump's Washington, D.C. criminal case impose a gag order limiting what he can say about prosecutors, court staff, as well as "reasonably foreseeable" witnesses.

However, the Daily Caller reported this week that Trump is challenging the order on constitutional grounds. 

Brief says  judge can't "muzzle the core political speech" of a presidential candidate

According to the website, the former president's attorneys told an appellate court on Wednesday that District Court Judge Tanya Chutkan "lacks the authority to muzzle" to muzzle their client's speech.

That argument appeared in a brief that maintained Chutkan "cannot silence President Trump based solely on the anticipated reaction of his audiences."

"The district court lacks the authority to muzzle the core political speech of the leading candidate for President at the height of his re-election campaign," brief insisted.

"President Trump is entitled to proclaim, and the American public is entitled to hear, his core political messages," it continued.

Ban on mentioning potential witnesses said to be "unconstitutionally vague"

Moreover, the brief pointed to the right enjoyed by "tens of millions of Americans to engage in and hear core political speech in the middle of an ongoing Presidential campaign."

It also took particular issue with the gag order's prohibition on Trump referencing potential witnesses, something the brief slammed as being "unconstitutionally vague."

"The discovery in this case comprises nearly 13 million pages and references hundreds of individuals," Wednesday's brief declared.

"It is anyone’s guess which witnesses may be 'reasonably foreseeable' at this stage, and this future-looking standard invites impermissible enforcement-by-hindsight," the document added.

ACLU side with Trump in opposing gag order

Interestingly, Trump's gag order has drawn criticism from the American Civil Liberties Union (ACLU), which fiercely criticized the former president while he was in office.

The Hill reported late last month that the ACLU filed a brief complaining that Chutkan's ruling violated the Constitution's First Amendment.

It asserted that "Trump retains a First Amendment right to speak, and the rest of us retain a right to hear what he has to say."

"The entire order hinges on the meaning of the word 'target.' But that meaning is ambiguous, and fails to provide the fair warning that the Constitution demands, especially when, as here, it concerns a prior restraint on speech," it asserted, echoing some of the claims made in the brief put forward this week by Trump lawyers.