Commissioner Roger Goodell sent the Minnesota Vikings star a letter on Thursday advising him of his reinstatement. Peterson missed most of last season while facing child abuse charges in Texas.
Goodell wrote that Peterson will have to fulfil all the obligations of his plea deal that reduced a felony charge to a misdemeanour.
Goodell also told Peterson he would have to continue attending counselling while adhering to the league's new personal conduct policy to avoid further discipline.
"Any further violation of the personal conduct policy by Peterson would result in additional discipline, which could include suspension without pay or banishment from the NFL," the league said.
Peterson's agent has said the star running back wants to play elsewhere next season. But the Vikings say they have no plans to trade him.
"We look forward to Adrian re-joining the Vikings," the team said in a statement issued after the announcement.
Peterson was indicted on abuse charges after inflicting injuries on his 4-year-old son with a wooden switch. He played the opener against St. Louis, then sat out the remaining 15 games of the season while tangling with the league over the discipline.
Harold Henderson, a league-appointed arbitrator, rejected Peterson's appeal and upheld the suspension in December. The NFLPA's petition in federal court to overrule Henderson was granted by U.S. District Judge David Doty, who ordered the appeal back to the NFL for re-arbitration. The league promptly appealed Doty's decision to a higher court.
The 8th Circuit Court of Appeals won't hear that case for months, so those proceedings will be merely for principle in the ongoing dispute between NFL owners and players over protocol and fairness of the personal conduct policy.
The league essentially tabled Peterson's suspension in February after Doty's ruling, putting him back on the exempt list to allow the Vikings to communicate with him, but the announcement Thursday means he's finally in the clear to take the field again.
The question, then, is what colours he'll be wearing this fall.
Despite several cordial meetings with Vikings officials, Peterson's public stance on returning to the only NFL team he has ever played for has been uneasy at best.
In his statement the day of Doty's ruling, Peterson thanked fans, the NFLPA, the union's lead lawyer and his agents but never mentioned the Vikings. One of his agents, Ben Dogra, took the stance a step further in March by declaring that Peterson no longer wanted to return to Minnesota, setting up a stare-down of sorts between the two sides.
"You make tough choices in life. We clearly understand he's under contract with the Vikings. After several discussions and much thought, I believe that it's not in his best interest to resume his career in Minnesota," Dogra said last month. "It might be best for all parties involved for him to resume his career elsewhere."
Vikings general manager Rick Spielman has told Dogra he doesn't plan to release Peterson, who recently turned 30.
"They have not given us one compelling reason why it's in his best interest to remain as part of the Minnesota Vikings," Dogra said.
The Vikings have leverage with Peterson's contract, which covers the next three years including a $12.75 million salary for 2015. None of the remaining money on the deal, however, is guaranteed.
If they're serious about not trading the franchise player, the Vikings could conceivably sit tight all spring and summer and not have to pay Peterson at all, given that player paychecks don't go out until the regular season games begin.
Peterson has a $250,000 workout bonus in his contract, but if he's not interested in playing for the Vikings anymore, he's surely not going to attend their off-season training program when he lives near Houston. He'd be subject to fines if he were to skip the mandatory minicamp in June.
AP Pro Football Writer Dave Campbell contributed to this report.
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