Billy Hunter and Derek Fisher delivered a letter to the players on Monday.

"With no labor union in place, it is our sincere hope that the NBA will immediately end its now illegal boycott and finally open 2011-12 season. Individual teams are free to negotiate with free agents for your services.

"If owners ... continue present course of action, it is our view they subject themselves to significant antitrust liability."

The letter also confirms that the union can no longer bargain with owners.