While the ruling allows Saints linebacker Vilma, banned for the 2012 season, Saints defensive end Will Smith, Cleveland linebacker Scott Fujita and free agent defensive lineman Anthony Hargrove to play immediately, it does not permanently void their suspensions.
Still, the ruling comes just two days before the first full slate of NFL games this season and is a setback for Commissioner Roger Goodell and the league.
NFL spokesman Greg Aiello said Goodell would "make an expedited determination of the discipline imposed" for violating the league's bounty rule.
"Until that determination is made, the four players are reinstated and eligible to play starting this weekend," Aiello said.
Vilma tweeted: "Victory is mine!!!! -stewie griffin"
Added Fujita: "I'm overwhelmed with all the support. Thank you so much everyone. Can't tell you how much it means to me."
The ruling does not affect New Orleans coach Sean Payton, also suspended for the season, interim coach Joe Vitt (six games) or general manager Mickey Loomis (six games)
While the panel did not address the merits of the NFL's bounty investigation, it said Goodell overstepped his authority in hearing the players' appeals of their punishment for their roles in the Saints bounty program that paid cash bonuses for hits that injured opponents.
The panel's decision states that Special Master Stephen Burbank, not Goodell, should discipline players for receiving money from a pool that paid for big plays. Goodell's role, the panel said, should be limited to whether he can prove the players intended to injure opponents, which would fall in the category of conduct detrimental to the game. Players and coaches implicated in the bounty pool have testified under oath in a related federal court case they never intended to injure opposing players.
"Whether the commissioner tries to readdress the situation or not is his call," said Peter Ginsberg, Vilma's attorney. "We are certainly hoping the appeals board has made it clear the commissioner tried to grab jurisdiction and impose penalties over an area he does not have oversight. ... The factual record in the court makes it clear he has acted in a biased and inappropriate manner."
The Saints open their season at home against Washington on Sunday, while the Browns host Philadelphia.
Earlier this week, Saints interim head coach Aaron Kromer said Smith, who participated in training camp and the preseason before he began serving his four-game suspension on Monday, would be ready to play against Washington if available.
Vilma's status was not as clear. His season-long suspension began before training camp and he has been trying to work his way back from off-season surgery on his left knee.
Saints players had recently finished practice when they received word of the panel's ruling.
"It's huge," said Saints safety Malcolm Jenkins, a defensive captain. "Those are two huge leaders we've got. They're great players. We've got a talented team, but you add Will Smith and Jonathan Vilma, our talent level goes up that much. For our team, it's a break."
Even if Vilma could not play right away, Jenkins said his presence in the locker room and meetings would be valuable.
Fujita, who had been suspended three games, also was expected to be able to play right away.
Before learning the suspensions had been overturned, Browns coach Pat Shurmur said even though Fujita missed practice this week he would likely play in Sunday's opener against Philadelphia if he was eligible.
"I don't see any reason why he can't play," Shurmur said.
Fujita was barred from Cleveland's training facility this week, but he stayed in town and worked out on his own at nearby Baldwin Wallace University in the event the suspension was lifted. Fujita, who serves on the NFLPA's executive committee, had expressed confidence he would be on the field in Week 1. His return is welcome news to the Browns.
Hargrove, docked eight games, was released last month by Green Bay and was not currently with a team.
The panel consisted of retired federal Judge Fern Smith of San Francisco, retired federal Judge Richard Howell of New York, and Georgetown professor James Oldham. It met in New York last week to hear arguments from the NFL Players Association, which appealed Burbank's ruling that Goodell had the authority to hear and rule on the players' appeals of their suspensions. NFL attorneys had asked the panel to affirm Burbank's ruling, but the panel sided in large part with the union.