A federal judge in Minnesota has denied the NHL's latest attempt to throw out a class-action lawsuit by former players filed over head injuries.

The league had argued that the suit should be tossed because the issues raised by the former players were covered under the collective bargaining agreement with the players' union. U.S. District Judge Susan Richard Nelson wrote in a 47-page opinion Wednesday that the contract does not pre-empt legal action, in part because the players are retired and no longer subject to the CBA. Nelson also wrote that the subjects of the complaint are not spelled out in the CBA.

Dan LaCouture, Michael Peluso, Gary Leeman, Bernie Nicholls, David Christian and Reed Larson represent former players who say the NHL did not sufficiently protect or inform the players of the dangers when it comes to head injuries they suffered when they played.

Last year, the NHL filed to have the lawsuit dismissed based on statute of limitations. That was also denied.

Stuart Davidson, a lawyer for the players, called the order a "historic decision in American sports and labor law." The NHL did not immediately respond to a message seeking comment but was expected to issue a statement on the ruling.

University of Illinois labor expert Michael LeRoy said the court's opinion is significant because the case remains alive and he wondered if the NHL might move toward settling this case like the NFL did with its concussion lawsuit.

"The NHL had to try" to get the case dismissed on these grounds, LeRoy said. "But this crosses a bridge and it leads to the courthouse, not away from the courthouse."