Hunter Biden, the son of US President Joe Biden, has been indicted on three federal firearms-related charges, according to a court filing.
It came after efforts to reach a plea deal failed, leading to the first-ever prosecution of a sitting president's child.
The indictment, in a Delaware federal court, is tied to the possession of a gun while using narcotics.
The charges mean the courtroom drama will play out during the 2024 US presidential campaign as Mr Biden, 80, seeks reelection in a likely rematch with his predecessor Donald Trump, 77, who is facing four upcoming criminal trials.
Sky News's US correspondent Mark Stone described the indictment as a "significant step" that likely resulted in a "head in hands" moment for the US president.
"Another day, another extraordinary moment in the American political journey. Whether it's Trump or whether it is Biden, both sides now embroiled in their own very different legal wranglings."
Two counts are tied to the president's son allegedly filing a form claiming he was not using illegal drugs at the time he purchased a revolver in October 2018, while the third alleges he possessed a firearm while using a narcotic.
The 53-year-old has also been under investigation for his business dealings, with the special counsel overseeing the case having indicated charges of failure to pay taxes on time could be filed in Washington or in California, where he lives.
A gun possession charge against Biden had previously been part of a plea deal that also included guilty pleas to misdemeanour tax charges, but the agreement fell apart during a court hearing in July when a judge raised questions about its unusual provisions.
Defence lawyers have argued a part of the deal sparing Mr Biden prosecution on the gun count if he stays out of trouble remains in place - it includes immunity provisions against other potential charges.
Lawyers indicated they would fight additional charges filed against him. Prosecutors, however, maintain the agreement never took effect and is now invalid.
Biden's lead counsel, Abbe Lowell, said the indictment "presents a grave threat to our system of justice."
He added: "We believe these charges are barred by the agreement the prosecutors made with Mr Biden, the recent rulings by several federal courts that this statute is unconstitutional, and the facts that he did not violate that law, and we plan to demonstrate all of that in court."
Republicans pursue impeachment inquiry against president
It comes as Republicans pursue an impeachment inquiry over the business dealings of the president's family, largely over his son's business dealings.
They have obtained testimony about how Biden used the "Biden brand" to drum up work overseas, but they have not produced hard evidence of wrongdoing by the president.
US House Speaker Kevin McCarthy has said he is directing committees to open a formal investigation into what he called a "culture of corruption" around the first family.
He said over the past few months "House Republicans have uncovered serious and credible allegations into President Biden's conduct".
Democrats described the move as "absurd", while the White House called it "extreme politics at its worst."