Bergdahl, who walked off his post in Afghanistan in 2009 and was held captive by the Taliban and their allies for five years, is due to face a court-martial on desertion and misbehavior in April. The misbehavior charge carries a maximum sentence of life in prison.
In 2014, the Obama administration exchanged five Taliban prisoners for Bergdahl, a controversial decision some Republican lawmakers said jeopardized national security. The administration was criticized for not obeying a statute requiring it to notify Congress 30 days before a prisoner transfer, which the administration said it could not have done without risking Bergdahl's life.
Trump in particular has repeatedly called Bergdahl a traitor.
"We're tired of Sergeant Bergdahl, who's a traitor, a no-good traitor, who should have been executed," Trump told a crowd in Las Vegas in October 2015.
"Thirty years ago he would have been shot," the now-president-elect said, according to Fox News. He would make similar statements throughout his campaign.
A "Trump Defamation Log" being kept by Bergdahl's defense has recorded 40 cases so far, AP reports.
Bergdahl's lead defense lawyer, Eugene Fidell, told the New York Times if the case is still pending on January 20, Inauguration Day, he will file a motion to have it dismissed on the grounds that a fair military trial will be impossible with Trump as commander in chief.
"I have grave concerns as to whether Sergeant Bergdahl can receive a fair trial given the beating he has taken over many months from Mr. Trump, who will be commander in chief, as well as Senator [John] McCain's call for a hearing in case Sergeant Bergdahl is not punished," Fidell said.
Bergdahl walked off his post in remote Afghanistan in order to draw attention to what he called dangerous decisions by his superior officers and to get an audience with a top commander, he claims. Others have accused him of desertion or of wishing to join the Taliban.
An Army officer leading an investigation into the incident concluded in 2015 that Bergdahl was roughly telling the truth and recommended no jail time and that his case be handled within a military system that deals with the equivalent of civilian misdemeanors. The advice was not followed. A sanity board found that was suffering from a "severe mental disease or defect" when he made the decision to leave his post, the New York Times reported.
"People in the military do what their commanders tell them to do," Florida International University law professor Eric Carpenter told AP. This means there's a risk that military jurors will be inclined to punish Bergdahl regardless of the evidence because they think that's what their commander-in-chief wants, he said.
The White House and the Department of Justice have not commented on the pardon.
