• Lawyers for Hunter Biden on Thursday asked federal judges in California and Delaware to dismiss the criminal tax and gun cases against him in their courts.
• Biden's lawyers cited a recent opinion by Supreme Court Justice Clarence Thomas and the dismissal this week of the criminal classified documents case against former President Donald Trump by Judge Aileen Cannon.
• Defense lawyers pointed to those rulings in arguing that the appointment of U.S. Attorney David Weiss as special counsel for prosecutions of Biden was unconstitutional.
• Hunter Biden is the son of President Joe Biden, who as of now plans to face Trump in November's election.

Lawyers for Hunter Biden on Thursday asked federal judges in California and Delaware to dismiss the criminal tax and gun cases against him in their courts, citing a recent opinion by Supreme Court Justice Clarence Thomas and the related dismissal this week of the criminal classified documents case against former President Donald Trump.

Biden's lawyers in motions filed in both courts pointed to those two opinions — which questioned the legality of the appointment of special counsel Jack Smith to prosecute Trump — in arguing that the appointment of U.S. Attorney David Weiss as special counsel for prosecutions of the son of President Joe Biden was unconstitutional.

The motions follow the ruling Monday by Florida federal court Judge Aileen Cannon tossing out Smith's prosecution of Trump over his retention of classified documents after leaving the White House.

Cannon, who herself cited Thomas' recent concurring opinion in another Trump case, ruled that Smith's appointment as special counsel violated the Appointments Clause of the U.S. Constitution. Smith on Wednesday filed an appeal of Cannon's decision.

"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," Hunter Biden's lawyers wrote in their filings Thursday.

However, a key difference between Smith and Weiss is that Smith was a private citizen when he was tapped as special counsel by Attorney General Merrick Garland, while Weiss was already a Senate-confirmed U.S. Attorney for Delaware when Garland named him special counsel.

But Biden's lawyers in their motion suggested that the difference is not relevant.

"The constitutional flaw at the center of the Special Counsel's appointment is that Congress
has not established the office of a Special Counsel," those lawyers wrote.

"Given that Congress requires a U.S. Attorney to be nominated by the President and confirmed by the Senate, it makes no sense to assume that Congress would allow the Attorney General to unilaterally appoint someone as Special Counsel with equal or greater power than a U.S. Attorney," the filing says. "That is what has been attempted here."

CNBC has requested comment from Weiss.

Biden, 54, was convicted in Delaware federal court in June of three felony counts related to his purchase of a handgun in Delaware in 2018 while being a user and addict of crack cocaine. The motion filed Thursday in that court asks for the conviction to be tossed out and the case dismissed.

He is awaiting trial in Los Angeles federal court on federal tax crime charges, which Biden's lawyers likewise are asking a judge there to toss out.

Both motions by Biden note that his lawyers previously, and unsuccessfully, argued that Weiss was improperly appointed special counsel in violation of Department of Justice regulation, and because he relied on funding that did not apply to the special counsel.

"But the motion Mr. Biden brings now is different and builds on recent legal developments," his lawyers wrote.

The motion notes that on July 1 the Supreme Court said that Trump had presumptive immunity from criminal prosecution for so-called official acts as president. That ruling related to Smith's pending prosecution of Trump in Washington, D.C., federal court for crimes associated with Trump's attempt to reverse his loss to President Biden in the 2020 election.

In a concurring opinion with the majority ruling in the Supreme Court, Justice Thomas suggested that Smith's appointment as special counsel "may violate our constitutional structure."

"In this case, the Attorney General purported to appoint a private citizen as Special Counsel to prosecute a former President on behalf of the United States," Thomas wrote. "But, I am not sure that any office for the Special Counsel has been 'established by Law,' as the Constitution requires."

Thomas wrote that "lower courts" should answer whether special counsels are allowed by the Constitution before proceeding in the cases against Trump.

Judge Cannon on Monday did just that in her ruling tossing out the classified documents case against the former president, which cited Thomas' concurring opinion in the Supreme Court case several times.

Cannon wrote that Smith's appointment violated the Appropriations Clause because as a rule says " 'officers of the United States — whether 'inferior' or 'principal' — must be appointed by the President and confirmed by the Senate."

Smith, like Weiss in Biden's cases, was appointed by Attorney General Merrick Garland.

Cannon also ruled that the use by Smith's office of a permanent funding appropriation also violated the Appropriations Clause of the Constitution.

Biden's lawyers cited Cannon's ruling on that point in arguing that Weiss's use of a permanent funding appropriation likewise renders his indictment of Biden unconstitutional.