The NFL breached its agreement with the league's players' union when it negotiated new television deals a federal judge ruled on Tuesday, a decision that could impact on an eventual lockout.
The union had argued that the structure of the NFL's contracts with television partners was designed to give it a $4 billion stockpile of cash to help it through any lockout.
The current Collective Bargaining Agreement between the league and the union (NFLPA) expires on Thursday.
U.S. District Court Judge David Doty agreed the deals had breached parts of the CBA and ordered that a hearing should be held to consider damages to be paid to the union and any injunction on use of the resources.
No date has been set for that hearing.
"This ruling means there is irrefutable evidence that owners had a premeditated plan to lock out players and fans for more than two years," the NFLPA said in a statement.
"The players want to play football. That is the only goal that we are focused on."
The ruling related to the NFL's agreements with television companies FOX, NBC, ESPN, CBS and DirecTV, which the union argued were designed to give it resources to use in the event of a work stoppage.
Those contracts included 'work stoppage provisions' which had not been in previous contracts.
NFL spokesman Greg Aiello said: "as we have frequently said, our clubs are prepared for any contingency, this decision included.
"Today's ruling will have no effect on our efforts to negotiate a new, balanced, labor agreement."
Owners and the NFLPA continue to negotiate in Washington ahead of Thursday's deadline but no agreement appears imminent.