NFL Commissioner Roger Goodell imposed the suspension after the "Deflategate" scandal stemming from last season's playoff game.
"Our role is not to determine for ourselves whether Brady participated in a scheme to deflate footballs or whether the suspension imposed by the commissioner should have been for three games or five games or none at all," Judge Denny Chin and Judge Barrington Parker wrote in their majority opinion released today. "Nor is it our role to second-guess the arbitrator's procedural rulings."
Instead, the appeals court judges explained that they determined Brady's arbitration proceedings and award met the minimum legal standards.
"We hold that the Commissioner properly exercised his broad discretion under the collective bargaining agreement and that his procedural rulings were properly grounded in that agreement and did not deprive Brady of fundamental fairness," the judges' majority opinion stated.
Out of the three-judge panel, one dissented. Judge Robert Katzmann called Goodell's explanation of Brady's discipline "murky." Katzmann said the commissioner relied on an "inapt analogy to the league's steroid policy" when handing down what the judge called an "unprecedented four-game suspension."
"It is ironic that a process designed to ensure fairness to all players has been used unfairly against one player," Katzmann wrote.
In September, federal judge Richard Berman in New York overturned Tom Brady's four-game suspension a week before the team's first game last season. Berman said Brady's punishment "cannot reasonably" be the equivalent of the four-game suspension handed down to players who use steroids, as noted in the collective bargaining agreement with players. The steroid policy details testing procedures, an appeal right, discovery process, and burdens and standards of proof. The NFL said at the time that it "respectfully" disagreed with Berman's decision and intended to appeal that decision.
Brady's suspension was first handed down in May last year, along with a $1 million fine levied on the New England Patriots and the loss of the club's first-round selection in the 2016 draft and fourth-round in the 2017 draft. Brady's suspension was then upheld by the NFL in July.
The punishment revolves around the deflation of footballs used during the AFC Championship game against the Indianapolis Colts on Jan. 18, 2015. The Patriots won that game 45-7, then went on to win the Super Bowl on Feb. 1 against the Seattle Seahawks.
A spokesman for the Patriots declined to comment to ABC News.
The NFL Players Association said in a statement that it is “disappointed” by the court’s decision.
“We fought Roger Goodell's suspension of Tom Brady because we know he did not serve as a fair arbitrator and that players' rights were violated under our collective bargaining agreement,” the association said in a statement. “Our union will carefully review the decision, consider all of our options and continue to fight for players' rights and for the integrity of the game.”