One day after President Donald J. Trump issued a sweeping legal reprieve to all of the nearly 1,600 people charged in connection with the attack on the Capitol on Jan. 6, 2021, some of the defendants started having their cases dismissed or even began to be released from custody.

By Tuesday afternoon, two of the country’s most prominent far-right extremists — Enrique Tarrio of the Proud Boys and Stewart Rhodes of the Oath Keepers militia — who played central roles in the Capitol attack had been set free.

Mr. Tarrio, who was serving a 22-year term for a conviction on charges of seditious conspiracy, received a pardon from Mr. Trump and walked out of a prison in Pollock, La. Mr. Rhodes, who was serving an 18-year term on similar charges, had his sentence commuted to time served and was freed from a prison in Cumberland, Md.

Defense lawyers said that another member of the Proud Boys, Joseph Biggs, who was one of Mr. Tarrio’s co-defendants, was also released after Mr. Trump commuted his sentence. Mr. Biggs had been serving 17 years in prison following his own conviction on seditious conspiracy charges.

Additional members of the Proud Boys and Oath Keepers were expected to be freed in the coming days.

Defendants have also started to be released from the local jail in Washington, where several rioters have been held in recent years in a special area nicknamed the “patriot wing.” On Monday night, two brothers from Pennsylvania, Matthew and Andrew Valentin, were set free, only days after being sentenced to two and a half years each on charges of assaulting the police.