Washington DC - A federal judge on Monday dismissed the criminal cases brought against former FBI director James Comey and New York Attorney General Letitia James, two prominent foes of President Donald Trump.

Judge Cameron Currie threw out both cases on the grounds that the prosecutor handpicked by Trump who brought the charges was unlawfully appointed.

Comey (64) was charged in September with making false statements to Congress in what has been widely seen as a campaign of retribution by the president against his political opponents.

James (67), a Democrat who successfully prosecuted Trump for fraud, was indicted the next month on one count of bank fraud and a second one of making false statements to a financial institution.

Both indictments were brought by an inexperienced prosecutor, Lindsey Halligan, who was a former personal attorney to Trump.

Comey's indictment came after the US attorney for the Eastern District of Virginia, Erik Siebert, stepped down after reportedly telling Justice Department leaders that there was insufficient evidence to charge him.

Attorney General Pam Bondi replaced Siebert with Halligan, and she brought the case to a grand jury and secured an indictment.

Top federal prosecutors are generally subject to Senate confirmation, and Currie ruled that Halligan was unlawfully appointed.

"The Attorney General's attempt to install Ms. Halligan as Interim US Attorney for the Eastern District of Virginia was invalid," the judge said.

"And because Ms. Halligan had no lawful authority to present the indictment, I will grant Mr. Comey's motion and dismiss the indictment without prejudice."

She made a similar ruling in James's case.

Dismissing the indictment without prejudice leaves open the possibility of the charges being filed again although the statute of limitations in the Comey case may have since expired.

Comey and James also sought to have the indictments dismissed on the grounds they were a vindictive prosecution. Those arguments were heard by a different judge.

Another Trump critic, his former national security advisor John Bolton, has been indicted on 18 counts of transmitting and retaining classified information.

Comey was appointed to head the FBI by then-President Barack Obama in 2013 and was fired by Trump in 2017.

The charges against Comey came days after Trump publicly urged Bondi to take action against the former FBI director and others he sees as enemies – a stunning departure from the principle that the Justice Department must be free from White House pressure.

Since taking office in January, Trump has taken a number of punitive measures against perceived enemies, purging government officials he deemed to be disloyal, targeting law firms involved in past cases against him, and pulling federal funding from universities.