In a flurry of legal filings, special counsel David Weiss’s office responded Tuesday to Hunter Biden’s December motions to dismiss federal firearms charges filed against him in Delaware, on what his attorneys said in a statement a were “unprecedented, unconstitutional” charges that violated a diversion agreement signed in 2023.

In court documents, federal prosecutors argued that the gun charges facing the president’s son were not part of a politicized and “selective and vindictive prosecution” as argued by the defense. They said the evidence, including Hunter Biden’s own words in his 2021 memoir, Beautiful Things, recovered text messages and the presence of cocaine residue on a leather firearm pouch demonstrated he had unlawfully possessed a firearm during a period when he struggled with drug addiction.

“The charges in this case are not trumped up or because of former President Trump—they are instead a result of the defendant’s own choices and were brought in spite of, not because of, any outside noise made by politicians,” prosecutors said in the filings.

Hunter Biden was indicted by a federal grand jury in September on three felony charges related to his alleged unlawful purchase and possession of a Colt Cobra .38 Special revolver in October 2018 while he was a drug user. He pleaded not guilty to all three charges in 2023.

Federal prosecutors also argued that the diversion agreement — which would have immunized Biden from prosecution on federal gun charges if he agreed not to use drugs or possess a firearm — was never approved by U.S. Probation and never went into effect.

But Hunter Biden’s legal counsel maintains that the diversion agreement is legally binding and still valid. The agreement, along with a plea deal related to tax charges, unraveled in federal court in July after a judge questioned the terms and whether the agreement would allow Hunter Biden to avoid potential future charges.

Hunter Biden’s attorneys also leaned heavily on a Second Amendment argument that has been favored by his father’s political opponents stemming from the Supreme Court’s 2022 decision in the case New York State Rifle & Pistol Association v. Bruen. That case led to a new legal test laid out by Justice Clarence Thomas, which requires judges to weigh whether state and federal gun laws are “consistent with the nation’s historical tradition of firearm regulation.”

In their motion to dismiss, Biden’s counsel argued that the statute federal prosecutors used to charge him with the unlawful possession of a firearm as a drug user was unconstitutional because they cannot prove that he was using drugs at the moment of the transaction to purchase the firearm.

In response, prosecutors for the special counsel stated that the government has evidence that Hunter Biden engaged in drug use while he possessed the firearm, and “Anglo American law has long recognized the government’s ability to restrict access to firearms” for those whose possession would pose a risk to public safety.

Federal prosecutors also argued that the special counsel’s appointment in itself and funding for the investigation was lawful after Hunter Biden’s attorneys asserted that it had not been approved by Congress and therefore violated the Appropriations Clause.

The Justice Department has the authority to “designate any officer of the Department to represent the United States in court,” prosecutors responded, and its designated congressional appropriation covers the independent investigation.

The ongoing investigation into Hunter Biden, led by Weiss, had spanned five years over the course of both the Trump and Biden administrations. Weiss was appointed U.S. attorney for Delaware by former President Donald Trump and named special counsel by Attorney General Merrick Garland in 2023.

Hunter Biden also faces federal charges in California in a second indictment secured by special counsel Weiss’ office for his alleged failure to file and pay taxes, evasion of assessment and filing a false or fraudulent tax return. Prosecutors say Hunter Biden engaged in a “four-year scheme” to avoid paying at least $1.4 million in federal taxes. He  pleaded not guilty to nine federal tax charges this month and faces up to 17 years in prison if convicted .

Catherine Herridge contributed to this report.