WASHINGTON — Hunter Biden pushed back Monday against gun charges filed against him, challenging the case on multiple fronts as unconstitutional and politically motivated days after he was hit with new tax charges.

His defense attorney argued the gun case should be tossed out because an appeals court has found the law violates the Second Amendment under new standards set by the Supreme Court. Abbe Lowell also contended the charges against Hunter Biden violated immunity provisions that prosecutors agreed to in a plea deal they abandoned after Republicans slammed it as a “sweetheart deal.”

“These charges are unprecedented, unconstitutional and violate the agreement the U.S. Attorney made with Mr. Biden,” Lowell said in a statement. “This is not how an independent investigation is supposed to work, and these charges should be dismissed.”

The flurry of court documents comes as Hunter Biden faces charges in two states headed toward trial while his father, President Joe Biden, runs for reelection.

Prosecutors, for their part, have previously said that any immunity provisions are now defunct along with the rest of the plea agreement that imploded over the summer. Special counsel David Weiss didn’t immediately respond to Hunter Biden’s other arguments, which also include a contention that Weiss wasn’t properly appointed. The prosecution has until Jan. 16 to respond.

The original plea deal negotiated between the prosecution and the defense contained immunity provisions meant to bring “closure and finality” to the investigation and protect Hunter Biden from being charged for “the same conduct” if Donald Trump was reelected, his previous lawyer said in court documents.

Under the agreement, Hunter Biden would have pleaded guilty to misdemeanor tax charges and avoided a full prosecution on a gun count if he stayed out of trouble for two years. He’s accused of having a gun for 11 days in 2018, a period where he has acknowledged using drugs. It’s illegal for “habitual drug users” to own guns.

Since its dissolution of that deal, though, prosecutors have filed three felony gun counts in Delaware and, last week, nine tax counts in California alleging he schemed to avoid paying $1.4 million in taxes between 2016 and 2019.

Republicans have said the new charges show the original deal was too lenient. Lowell, though, argued Weiss “buckled under political pressure to bring more severe charges.”

Firearm charges like those Hunter Biden is facing are seldom filed as standalone counts in non-violent offenses. An appeals court, meanwhile, has struck down the law itself, finding people shouldn’t lose their right to bear arms due solely to past drug use.

That decision from the Louisiana-based 5th Circuit came after the Supreme Court set new standards for gun laws in 2022, leading to upheaval in the nation’s gun-law landscape. President Biden called the Supreme Court opinion “deeply disappointing.”

The 5th Circuit ruling doesn’t directly affect Hunter Biden’s case since it was made in another part of the country, but the federal appeals court overseeing Delaware has made another ruling that people convicted of nonviolent crimes shouldn’t be barred from gun possession for life.