The NHL says it will postpone its plans for realignment because the players association wouldn't approve it in time for next year's schedules. (The union has taken to Twitter to deny it balked at the plan.)
This is tied to travel, which is subject to collective bargaining, but only indirectly. So it's not clear to me that this is something the union should have any say over. The league says it will pursue all avenues to preserve its rights, but it says it's too late for next season.