Minnesota Judge says concussion lawsuit against NHL can proceed after refusing to dismiss a lawsuit filed by ex-players accusing the National Hockey League to protect them from head injuries while withholding information about the long-term effects of concussions.

Six retired players filed the class-action lawsuit with similar claims as the legal action brought against the National Football League, which has resulted in an estimated $1 billion in settlements with thousands of the league’s former athletes.

In a 47-page opinion made on Monday and unsealed on Wednesday, U.S. District Judge Susan Nelson declined to dismiss the case against the league, setting the state for it to proceed to a potential trial.

However, the door was left open for the lawsuit to be dismissed at a later stage, depending on what evidence emerges.

Nelson rejected arguments from attorneys for the NHL that protections against concussions should be dealt with in collective bargaining agreements, or CBAs, that would make the issues with the players union not decided in court.

“Even if some or all of plaintiffs were subject to a CBA at the time” they suffered their head injuries, the league “acknowledges that different versions of the CBAs contain different language,” Nelson wrote.

“There are major fact questions that cannot be resolved until a fuller record is developed” as the case proceeds, added Nelson.

Nelson’s ruling follows a similar decision last year, when she dismissed arguments by NHL’s attorneys to throw the case out of court.

“Based upon our review of Judge Nelson’s opinion, with which we respectfully disagree, the opinion merely defers to another day a resolution of the preemption issues underlying our motion,” NHL Deputy Commissioner Bill Daly said in a statement.

The retired players in the lawsuit accused the NHL of withholding information from them about the science linking brain trauma to long-term neurological problems, and failing to adopt measures to better protect players.

The league instead promoted a culture of violence, where fighting is central to the game where player inflict traumatic body-on-body hits against the sides of the ice rinks, said the the attorneys of the ex-athletes.

In 2013 some of the ex-players were sued and in 2014 their claims were consolidated with lawsuits filed by others.