Four years ago, when F.B.I. agents searched the Florida home of Jeremy Brown, a former Special Forces soldier, in connection with his role in the attack on the Capitol on Jan. 6, 2021, they found several illegal items: an unregistered assault rifle, two live fragmentation grenades and a classified “trip report” that Mr. Brown wrote while he was in the Army.

Mr. Brown was ultimately tried in Tampa on charges of illegally possessing the weapons and the classified material. And after he was convicted, he was sentenced to more than seven years in prison — even before his Jan. 6 indictment had a chance to go in front of a jury.

On Tuesday, however, federal prosecutors abruptly declared that because the second case was related to Jan. 6, it was covered by the sprawling clemency proclamation that President Trump issued on his first day in office to all of the nearly 1,600 people charged in connection with the Capitol attack.

And if a judge eventually agrees with that assessment, it could mean that Mr. Brown — whose Jan. 6 charges were already wiped out by the presidential pardon — will get to go free on his other case as well.

The Justice Department’s position with regard to Mr. Brown is not the first time it has said in recent days that separate criminal cases emerging from the investigation of Jan. 6 — especially those involving weapons discovered during searches — should be covered by Mr. Trump’s sweeping reprieves.

Ed Martin, the acting U.S. attorney in Washington, advanced that view on Tuesday in the case of another pardoned Jan. 6 defendant, Daniel Edwin Wilson.

Mr. Wilson, a Kentucky-based militiaman, pleaded guilty last spring to charges of conspiring to impede or injure officers at the Capitol. And as part of his plea, he also admitted to possessing illegal weapons and thousands of rounds of ammunition that were discovered during a search of his home as he was being investigated in connection with Jan. 6.

Just two weeks ago, Mr. Martin rejected the notion that the weapons charges were covered by Mr. Trump’s pardon. But he suddenly reversed himself this week, writing in a court filing that he had “received further clarity on the intent of the presidential pardon.”

“Under these circumstances,” Mr. Martin said, “the presidential pardon includes a pardon for the firearm convictions to which the defendant pled.”

Mr. Trump’s clemency proclamation says that anyone charged with or convicted of “offenses related to events that occurred at or near the United States Capitol on Jan. 6, 2021,” should either receive a pardon or have their case dismissed. And the Justice Department has increasingly taken the position that criminal behavior discovered during an investigation stemming from a suspect’s role in the Capitol attack is in fact related to Jan. 6.

Last week, for instance, the same U.S. attorney who handled Mr. Brown’s case moved to dismiss gun charges against another pardoned Jan. 6 defendant, Daniel Charles Ball. Only three days after Mr. Trump granted him clemency, Mr. Ball had been rearrested on an indictment accusing him of illegally possessing a firearm seized during a search of his home while he was being investigated for his Jan. 6 case.

In a similar fashion, federal prosecutors in Maryland asked a judge last Wednesday to release from prison Elias Costianes, a drug dealer who pleaded guilty in 2023 to illegally possessing a firearm even as he was awaiting trial on his Jan. 6-related charges.

Mr. Costianes recently began serving a two-year sentence on the weapons offense, but prosecutors have now sought to free him.

“After consulting with the Department of Justice’s leadership, the United States has concluded that the president pardoned Mr. Costianes of the offenses in the indictment,” a federal prosecutor wrote in court papers to a federal appeals court that Mr. Costianes had asked to let him go. “He should be immediately released from custody.”

The Justice Department has at times drawn lines, taking the view that not every crime committed by a pardoned Jan. 6 defendant is covered by Mr. Trump’s clemency decree.

Prosecutors, for example, have said they are unwilling to extend the pardon to a second case brought against Edward Kelley, a rioter from Tennessee who was convicted in November of plotting to assassinate the F.B.I. agents and police officers who investigated his Jan. 6-related case.

Mr. Kelley’s murder plot conviction, prosecutors wrote in a court filing last week, was simply not related to the Capitol attack.

“This case is about the defendant’s entirely independent criminal conduct in Tennessee, in late 2022, more than 500 miles away from the Capitol,” they said.

Mr. Martin’s office in Washington is also sticking — at least for the moment — by its plans to prosecute a pardoned rioter named Taylor Taranto. In June 2023, Mr. Taranto was arrested near the home of former President Barack Obama and the police found a cache of weapons, ammunition and materials that could be used to make explosives in his van.

Last month, following the instructions laid out in Mr. Trump’s pardon proclamation, Mr. Martin dismissed all of the Jan. 6-related charges Mr. Taranto faced. But he declined to drop the weapons offenses stemming from events two years ago, even though all of the charges were contained in the same indictment.

“Taranto’s actions in June 2023 in Washington, D.C., were not offenses occurring at the U.S. Capitol on Jan. 6, 2021,” Mr. Martin wrote.