Minneapolis, MN (SportsNetwork.com) - The National Football League Players Association has filed a federal lawsuit in a Minnesota court, asking to have last week's ruling against suspended Vikings running back Adrian Peterson vacated.

NFL-appointed arbitrator Harold Henderson last Friday upheld the NFL's indefinite suspension of Peterson for violating the league's personal conduct policy. Henderson said the ruling was not unfair or inconsistent, as Peterson's initial appeal had suggested.

The NFLPA argued in its petition Monday that Henderson's decision "is contrary to the essence of the NFL-NFLPA Collective Bargaining Agreement; it defies fundamental principles of notice, fairness, and consistency; and it was rendered by an evidently partial arbitrator who exceeded the scope of his authority."

NFL commissioner Roger Goodell announced last month that Peterson would be suspended without pay at least through the remainder of this season after the star running back pleaded no contest to a charge of misdemeanor reckless assault for striking his 4-year-old son with a wooden tree branch in May.

The NFLPA, in a statement after the ruling, said it expected Peterson's appeal to be denied because of what it called Henderson's "relationship and financial ties to the NFL."

Henderson is a former longtime NFL executive who dealt mostly in player and labor relations during his time with the league.

The union, in its filing Monday, again reiterated its stance that the NFL "is making it up as it goes along," in reference to the league's decisions on suspensions related to the personal conduct policy.

Under the NFL suspension, Peterson will not be considered for reinstatement prior to April 15 and he will forfeit six game checks.

The union argued that Peterson was penalized under a revised personal conduct policy issued in late August, months after the incident occurred.

The NFL beefed up the language in its policy in response to mounting criticism over the Ray Rice case. Rice won his appeal of an indefinite suspension levied by the commissioner in September for punching his now-wife in an Atlantic City Casino back in February.

Goodell and NFL owners last Wednesday announced a revised policy on personal conduct, doing so, the NFLPA said, without the union's input. However, the CBA that was agreed upon in August 2011, gives the commissioner's office the power to institute personal conduct penalties.

On Monday, ABC News also broadcast audio tape of a phone conversation between Peterson and NFL executive Troy Vincent.

Vincent, a former player and NFLPA president, told Peterson he would be subject only to a two-game suspension -- which was the maximum penalty for a first-time offender under the old policy and the initial penalty Rice was given for his transgression until videotape of Rice's incident surfaced.

During the appeal hearing, Vincent said he never promised Peterson anything and Henderson agreed in his ruling, saying Vincent didn't have the authority to make such promises.

The tape, which was part of the appeal process, has Peterson asking Vincent if he would only be penalized two games. Vincent responded, "Yeah," but added that Peterson would have to go through the process, which would include a hearing that the player did not attend.

Peterson hasn't played since the Vikings' season opener Sept. 7. The two-time NFL rushing champion was originally charged with reckless or negligent injury to a child, but pleaded no contest to the lesser misdemeanor offense after working out an agreement with the Montgomery County (Texas) district attorney.

The 2012 NFL MVP avoided jail time and was placed on probation while receiving a $4,000 fine and an order to perform 80 hours of community service.