Minneapolis, MN (SportsNetwork.com) - A federal judge on Thursday overturned an appeal ruling made against suspended Minnesota Vikings running back Adrian Peterson, potentially opening the door for him to be reinstated earlier than expected.

The NFL, following another public rebuke over the discipline of one of its players, said it will appeal the decision made by U.S. District Judge David S. Doty, sending the case to the 8th Circuit Court of Appeals.

The NFL returned Peterson to the commissioner's exempt list pending further proceedings with the arbitrator who ruled against the running back in December or a determination by the 8th Circuit Court.

Peterson was initially placed on the exempt list after he was charged with hitting his 4-year-old son with a tree branch in May.

After reaching a plea agreement in the case, Peterson was suspended by NFL Commissioner Roger Goodell in November for violating the league's personal conduct policy.

The suspension was based on a more stringent player conduct policy that was agreed upon after the actions that led to the charges against Peterson.

Arguing that the policy shouldn't be retroactively applied in Peterson's case and saying the league was "making it up as it goes along," the NFL Players Association filed an appeal on behalf of the running back, which was denied by league-appointed arbitrator Harold Henderson.

The union then filed a federal lawsuit, leading to Doty's ruling on Thursday to have Henderson's ruling vacated.

The union called the decision "a victory for the rule of law, due process and fairness."

"Our collective bargaining agreement has rules for implementation of the personal conduct policy and when those rules are violated, our union always stands up to protect our players' rights," the NFLPA said in a statement. "This is yet another example why neutral arbitration is good for our players, good for the owners and good for our game."

Under terms of his suspension, Peterson will be considered for reinstatement as of April 15. His future with the Vikings is considered unclear, though the team said in a statement on Thursday that its focus is on welcoming him back when he's eligible to return.

"Today's ruling leaves Adrian's status under the control of the NFL, the NFLPA and the legal system, and we will have no further comment at this time," the Vikings said.

It was the second time in three months the NFL lost a case concerning the discipline of a player. In November, former Baltimore Ravens running back Ray Rice was reinstated after winning an appeal of his indefinite suspension for striking the woman who is now his wife in a casino elevator in Atlantic City last year.

In the Peterson case, the NFL said Goodell had the "broad discretion" under the collective bargaining agreement to impose the enhanced discipline under the new policy.

Doty, however, disagreed with the NFL's assertion and said Henderson exceeded his authority in the appeal ruling.

"Judge Doty's order did not contain any determinations concerning the fairness of the appeals process under the CBA, including the commissioner's longstanding authority to appoint a designee to act as hearing officer," the NFL said in a statement.

"Even so, we believe strongly that Judge Doty's order is incorrect and fundamentally at odds with well-established legal precedent governing the district court's role in reviewing arbitration decisions."

Peterson last played in the Vikings' season opener on Sept. 7. The two-time league rushing champion and 2012 NFL MVP pleaded no contest to a lesser misdemeanor offense after working out an agreement with the Montgomery County (Texas) district attorney.

He avoided jail time and was placed on probation while receiving a $4,000 fine and an order to perform 80 hours of community service.