At the Justice Department, spokeswoman Kerri Kupec said the Flynn case had been reviewed by Jeff Jensen, a federal prosecutor in Missouri.
“Through the course of my review of General Flynn’s case, I concluded the proper and just course was to dismiss the case," Jensen said in a statement.
"I briefed Attorney General Barr on my findings, advised him on these conclusions, and he agreed," Jensen added.
The move drew sharp attacks from critics of the President.
"Attorney General Barr has consistently acted for the personal and political benefit of President Trump, rather than fulfilling his duty as chief law enforcement officer of the United States," said Noah Bookbinder, the head of the ethics watch dog group Citizens for Responsibility and Ethics in Washington.
"AG Barr’s politicization is destroying the credibility of the Department," said Rep. Ted Lieu (D-CA).
At the White House, the President said it was the right choice.
"He was an innocent man," President Trump told reporters in the Oval Office. "Now in my book he’s an even greater warrior.”
That was a different tune from what Mr. Trump said in December of 2017, when Flynn plead guilty to lying about his contacts with the Russian Ambassador, during the transition period between President Trump's victory, and taking the oath of office.
The dispute stems from a January 24, 2017 interview with Flynn at the White House, in which FBI agents asked whether Flynn had urged the Russian Ambassador to the U.S. to not respond to sanctions levied by the Obama Administration over election interference in 2016.
"During the interview, FLYNN falsely stated that he did not ask Russia's Ambassador to the United States ("Russian Ambassador") to refrain from escalating the situation in response to sanctions that the United States had imposed against Russia," the plea bargain states, which Flynn agreed to.
Flynn was later fired from his post as National Security Adviser for lying about the matter to Vice President Mike Pence.