The Justice Department shelved an investigation into former President Joe Biden’s use of an autopen, a person briefed on the matter told NBC News.

Justice Department pardon attorney Ed Martin, the former “weaponization” czar, opened the probe while he was interim U.S. attorney for the District of Columbia. It wound down recently under Jeanine Pirro, the current U.S. attorney, who is a longtime Trump ally and former Fox News host.

The New York Times first reported the news.

The autopen case was never presented to a grand jury, unlike the case that Pirro’s office tried to bring forward last month against six members of Congress who participated in a social media video that urged members of the military and intelligence communities not to follow unlawful orders.

It is difficult to bring a criminal case when there is not even a readily identifiable and applicable criminal statute, the person briefed on the matter said.

The White House referred an inquiry about the matter to the Justice Department. A spokesman for Pirro’s office, citing Justice Department policy, said the office does not confirm or deny the existence of criminal probes.

President Donald Trump issued an executive order in June demanding a wide-ranging investigation into Biden and officials in his administration after he claimed that Biden’s aides used “autopen” signatures to hide Biden’s “cognitive decline.”

The Republican-led House Oversight Committee investigated Biden’s use of an autopen, writing in a report in October that some executive actions he signed with an autopen were “illegitimate,” because he suffered from mental decline and could have been unaware of the contents.

Trump, who has repeatedly claimed that Biden used an autopen on many of his executive orders, said in November that he was canceling executive orders signed using Biden’s autopen.

It’s unclear how often Biden used an autopen, as there is no official government record of when it is used. In a statement in June, Biden responded to Trump’s claims, saying, “Let me be clear: I made the decisions during my presidency.”

“I made the decisions about the pardons, executive orders, legislation, and proclamations,” he said in the statement. “Any suggestion that I didn’t is ridiculous and false.”

Biden’s use of the autopen was investigated as Trump has directed the Justice Department to investigate a number of his political foes since he returned to office.

The Justice Department tried to prosecute former FBI Director James Comey and New York Attorney General Letitia James. A federal judge tossed out the criminal charges against both in November.

It also sent out criminal subpoenas in January to various state and local government offices in Minnesota, including Gov. Tim Walz and Minneapolis Mayor Jacob Frey, claiming they conspired to impede law enforcement during its immigration operations there. Neither have been charged, and legal experts have widely condemned an investigation that they say is based on a flimsy legal premise and has a chilling effect on free speech.