By Jonathan Stempel

NEW YORK (Reuters) - The National Hockey League on Wednesday filed a lawsuit against its players union, seeking to restore a 20-game suspension against Calgary Flames defenseman Dennis Wideman that a "neutral" arbitrator later cut in half.

In a complaint filed in the U.S. District Court in Manhattan, the NHL said arbitrator James Oldham "applied his own brand of industrial justice" by ignoring the findings of Commissioner Gary Bettman, who upheld the original suspension, and substituting a shorter 10-game ban.

A lawyer for the NHL Players' Association had no immediate comment. Oldham did not immediately respond to a request for comment.

Wideman was suspended for cross-checking NHL linesman Don Henderson from behind with his stick during a Jan. 27, 2016 game with the Nashville Predators.

According to the league, the blow caused Henderson to fall face first onto the ice, leaving him with a concussion and unable to resume work as a linesman.

The players' union appealed the 20-game ban to Oldham, a Georgetown University law professor, as permitted under its collective bargaining agreement (CBA).

But the NHL said Oldham did not act as a "neutral discipline arbitrator" (NDA) in halving Wideman's ban, given the lack of "substantial evidence" that Bettman's decision was wrong.

"The NDA exceeded his authority under the CBA and applied his own brand of industrial justice by disregarding the standard of review set forth in the CBA," the complaint said.

In September, U.S. District Judge Richard Berman in Manhattan said National Football League Commissioner Roger Goodell may have administered his own "industrial justice" in suspending New England Patriots quarterback Tom Brady for four games over deflated footballs used in a championship game.

Berman voided that ban, but a divided federal appeals court in Manhattan restored it on April 25. Brady and the NFL players union are trying to overturn the latter ruling.

Wideman had served 19 games of the original 20-game suspension when Oldham ruled, and was to have been refunded the salary he was going to forfeit as a result of the longer ban.

The case is National Hockey League v National Hockey League Players' Association, U.S. District Court, Southern District of New York, No. 16-04287.

(Reporting by Jonathan Stempel in New York; Editing by Andrew Hay)