Atlanta, Georgia - Special counsel Jack Smith has appealed a ruling which dismissed ex-president Donald Trump's case over the mishandling of classified documents.

Federal judge Aileen Cannon, a Trump appointee, dismissed that case in mid-July, citing doubts about the legality of the Justice Department's appointment of Smith.

In a Monday brief filed in the 11th US Circuit Court of Appeals, Smith argued that Cannon's decision to throw out the case "conflicts with an otherwise unbroken course of decisions... and it is at odds with widespread and longstanding appointment practices in the Department of Justice and across the government."

The court of appeals "should reverse the dismissal order and remand for further proceedings," Smith concluded.

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Attorney General Merrick Garland appointed Smith to lead the investigation into the classified documents case in November 2022.

He was also tasked with leading the investigation into the events after the 2020 presidential election, including Trump's role in the storming of the US Capitol on January 6, 2021.

The Republican presidential nominee was indicted in the documents case last year, but the case stalled and had not been expected to begin before November's election.

Trump was accused of unlawfully storing highly sensitive information from his term as president from 2017 to 2021, as well as conspiring to obstruct the investigation by ordering associates to delete surveillance camera footage and hide boxes of documents.

In August 2022, federal investigators raided Trump's Mar-a-Lago mansion and seized several sets of documents classified as top secret.

He pleaded not guilty when the charges were presented in Miami last year.

A successful appeal could lead to the proceedings being reopened, but even if they do, a trial would not take place before the election.