It marks the first time federal prosecutors have dropped a case from about 450 filed against supporters of Donald Trump accused of assaulting the Capitol on 6 January.
Christopher Kelly was charged following an anonymous tip to the Federal Bureau of Investigation that allegedly included photos posted to Facebook of him at the Capitol.
In a motion filed on Tuesday, authorities wrote that the government and defence counsel discussed the merits of the case "and upon reflection of the facts currently known to the government, the government believes that dismissal without prejudice at this time serves the interests of justice".
The brief filing says Mr Kelly was arrested on 20 January, the day Joe Biden was inaugurated as president. While he appeared before the court several times, the case was dismissed "without prejudice" a day before he was due to reappear on 2 June.
No reason was given for the dismissal in the filing, but a spokesman for the Justice Department, Marc Raimondi, told Bloomberg the case was being dropped because the charges against Kelly were “not consistent with what has been the standard across the other investigations".
Mr Kelly was facing four charges including obstruction of an official proceeding, aiding and abetting, unlawful entry to restricted buildings or grounds, and violent entry and disorderly conduct.
Other alleged offenders were charged with more serious crimes like assaulting police officers or damaging property.
“This one was kind of an anomaly,” Mr Raimondi told the outlet. “Most folks that were charged just for being on the grounds were charged if there were additional offences, or some other serious charge.”
The FBI's informant also shared screenshots of messages posted to the Facebook account on 28 December saying: "When good men do nothing, evil triumphs. Evil, sin and sinful men must be opposed. God commands those who are good, not just to avoid evil but actively oppose it.’ Where will you be on 1/6?”
The affidavit also said the FBI also received photos purporting to show Mr Kelly outside the Capitol.