WASHINGTON >> President Joe Biden’s son, Hunter Biden, moved on Thursday to throw out his criminal conviction on gun charges and dismiss a separate case accusing him of tax evasion based on an argument that the special counsel prosecuting him was unlawfully appointed.

Biden’s lawyers cited a federal judge’s decision on Monday to dismiss the criminal case accusing former President Donald Trump of illegally retaining classified documents after leaving office.

Florida-based U.S. District Judge Aileen Cannon found the appointment of the special counsel in that case, Jack Smith, violated the U.S. Constitution because Congress had not given him the authority to pursue the case. Smith’s office is appealing.

“The Attorney General relied upon the exact same authority to appoint the Special Counsel in both the Trump and Biden matters, and both appointments are invalid for the same reason,” Biden’s lawyers argued in a court filing.

A different special counsel, David Weiss, secured Hunter Biden’s conviction last month in Delaware federal court on charges he lied about his illegal drug use to buy a gun.

Weiss is also leading a tax case against Biden that is scheduled to go to trial in September. Biden has pleaded not guilty in that case.

A spokesperson for Weiss did not immediately respond to a request for comment.

The move by Biden shows the potential ripple effects from Cannon’s decision to limit the attorney general’s ability to appoint a special counsel to handle politically sensitive investigations, a practice the U.S. Justice Department has used for decades.

It also presents the awkward dynamic of the president’s son relying on a ruling benefiting Trump, his father’s Republican opponent in the Nov. 5 presidential election.

Biden is likely to have a more difficult time challenging the special counsel because Cannon’s ruling focused on the fact that Smith was not in the U.S. government when appointed and had not been confirmed for the role by the Senate.

Before being named special counsel, Weiss was confirmed by the Senate to serve as the top federal prosecutor in Biden’s home state of Delaware during the Trump administration.

Biden previously challenged the appointment of Weiss on different grounds, efforts that were rejected by federal judges in both cases against him.

Another defendant charged as part of Weiss’ investigation, Alexander Smirnov, moved to invalidate the special counsel after the ruling in Trump’s case. Smirnov has pleaded not guilty to charges that he lied to the FBI when he claimed knowledge of a bribe to Joe Biden.