Adrian Peterson's suspension from the National Football League triggered a courtroom clash Friday over the extent of the NFL's power.

With Peterson watching silently, the hourlong hearing — the first in a lawsuit filed against the NFL in U.S. District Court in Minneapolis — gave attorneys for the league and the NFL Players Association (NFLPA) their first opportunity to make their case in person to Judge David Doty.

The players' union wants Doty to send the case back to an arbitrator to overturn the suspension the NFL handed down to the Vikings star nearly three months ago.

"They can't have a lawless system … where they just make it up on their own," said NFLPA attorney Jeffrey Kessler, referring to the NFL not abiding by its collective bargaining agreement.

In response, the NFL argued that the case doesn't belong in court, but rather in arbitration, a process that has already taken place regarding Peterson. Which side Doty agrees with is likely to have major ramifications not just for Peterson, but for other NFL players in disciplinary cases.

"I feel good," Peterson said to reporters afterward.

Outside the downtown courtroom, a less serious scene faced him as he and his wife, Ashley, greeted fans sporting purple jerseys or signs in support, shouting "MVP! MVP!"

"We love you, AP! You can always call Minnesota home!" one fan shouted.

Justin Pruden of St. Paul stopped by to show his support and to get a football signed by the star. "I don't support what he did," Pruden said of Peterson's whipping of his son, the root of the case. "But I don't think the NFL is treating him fairly."

Peterson, 29, who has houses in Eden Prairie and near Houston, hadn't been seen publicly in Minnesota since practicing with the Vikings last Sept. 12 before news broke of the grand jury indictment in his case.

"I feel like I got a fair hearing today. I just really appreciate all the support from my fans," he added outside the courtroom. "It feels good to be in Minnesota."

Asked if he would like to stay with the Vikings, he said, "Of course."

At the end of Friday's hearing, packed with about 40 reporters and a couple of Peterson's friends, Doty said he'd take the issue under advisement. There's no timeline for when he could make a decision, but he could overturn the arbitrator's decision, uphold the arbitration process, or send it back to arbitration.

The NFLPA is asking for a quick resolution so Peterson can resume his career. The league's new year, and free agency, starts March 10. The Vikings have said they'd like Peterson to return to the team in 2015, but have stopped short of saying that will happen once he's eligible to be reinstated.

Peterson was fined $4.1 million, or six weeks' pay, from his $11.75 million salary last year. His contract runs through the 2017 season, but there's no guaranteed money remaining. His salary for the 2015 season is $12.75 million and the Vikings face an associated $15.4 million salary cap hit. They could reduce the salary cap hit by reworking his contract or the Vikings could cut Peterson, making him a free agent.

Suspended until April

In September, news surfaced that Peterson had whipped his 4-year-old son with a switch, leaving the boy with bruises and scars. In September, a Texas grand jury indicted him on a felony charge of injury to a child.

After a brief reinstatement drew protest, he was placed on the league's exempt list Sept. 16. The union filed a grievance to have Peterson taken off the exempt list; it was denied. On Nov. 18, the NFL suspended Peterson after his no-contest plea to a misdemeanor charge of reckless assault.

His suspension lasts until at least April 15, if he fulfills requirements set by Commissioner Roger Goodell, such as counseling and therapy — something his attorneys argued against at Friday's hearing, saying the NFL has never required treatment, "as if the NFL was a sentencing judge."

"The [collective bargaining agreement] doesn't give the NFL that authority; they would like that authority," Kessler said, adding that NFL should bargain with players over that issue. "But what they can't do is just make up the rules unilaterally."

Appealing suspension

After Peterson appealed his suspension, an arbitrator in December upheld it, saying Peterson's conduct toward his son was "brutal" and "arguably one of the most egregious cases of domestic violence in this Commissioner's tenure."

The NFLPA argues that the arbitration decision violated the collective bargaining agreement and that arbitrator Harold Henderson, a former league official, was biased and exceeded his authority. The players' union also says that Peterson had no idea when he disciplined his son in May that Goodell would in August release a new policy calling for heavier discipline of players involved in domestic violence.

At Friday's hearing, Kessler cited the case of Baltimore Ravens player Ray Rice, caught on camera punching his now-wife senseless. Rice was suspended but a retired federal judge reinstated Rice in arbitration, holding that Goodell "lacked authority" under the union contract to impose a harsher penalty than called for by the policy in force at the time of the offense.

The NFL doesn't see it that way. "The facts of that case were very different," said league attorney Daniel Nash.

The NFL also has dismissed the union's claim that the arbitrator was biased as based on "supposed appearance of bias, as opposed to actual bias."

In one of Doty's few exchanges with both sides, the judge questioned the NFL's past practice of two-game suspensions — something the union has said would have been Peterson's punishment prior to Goodell's new policy.

"Doesn't that have some strength in being the 'law of the shop?' " Doty asked.

Nash answered that it's disputable that the two-game suspension is standard. He reiterated that there's a "high burden" for the courts to vacate the arbitrator's decision.

"We're not here resolving other labor grievances they might have," he said, "especially ones ruled against them."

Kelly Smith • 612-673-4141

Twitter: @kellystrib