Hunter Biden, the son of US President Joe Biden, was indicted on three federal firearms charges on Thursday, marking the first ever prosecution of a sitting president's child.
He is accused of lying about his drug use when he bought a firearm in October 2018, a period when he has acknowledged struggling with addiction to crack cocaine, according to the indictment filed in federal court in Delaware, the President's home state.
In the US, it is illegal under federal law to buy a gun while addicted to a controlled substance.
The younger Mr Biden has also been under investigation over his foreign business dealings.
The indictment was brought by David Weiss, who was elevated to special counsel status in August after investigating Hunter Biden's business dealings for years as the US attorney in Delaware. Mr Weiss was originally nominated by former president Donald Trump.
In addition to the gun charges, the special counsel has indicated that charges of failure to pay taxes on time could be filed in Washington or in California, where Hunter Biden lives.
Republicans have obtained evidence about how Hunter used the “Biden brand” to drum up work overseas, but have not produced hard evidence of wrongdoing by the President.
A gun possession charge against the younger Mr Biden had previously been part of a plea deal that also included guilty pleas to misdemeanour tax charges, but the agreement imploded during a court hearing in July when a judge raised questions about its unusual provisions.
Defence lawyers have argued that a part of the deal sparing Hunter Biden from prosecution on the gun count if he stays out of trouble should remain in place. It includes immunity provisions against other potential charges.
His lawyers have indicated they would fight additional charges filed against him.
For years, Hunter Biden has been the focus of attacks by Mr Trump and his Republican allies who have accused him of wrongdoing related to Ukraine and China, among other issues. He has worked as a lobbyist, lawyer, investment banker and artist, and has publicly detailed his struggles with substance abuse.
While Republican politicians have collected evidence that the President at times joined calls with his son's business associates, they have yet to produce evidence that the elder Mr Biden personally benefited.
Hunter Biden disclosed in December 2020 that Mr Weiss's office was investigating his tax affairs. He has denied wrongdoing.