Here is the NHL's official explanation for the ruling on Cam Atkinson's go-ahead goal in the third period:
At 6:58 of the third period in the Detroit Red Wings/Columbus Blue Jackets game, the NHL Situation Room initiated a review because the puck crossed the Red Wings goal line. The referee determined that the puck crossed the goal line and that Red Wings defenseman Brendan Smith pushed Blue Jackets forward Cam Atkinson
into the net causing the goal post to be dislodged.
According to rule 63.6 "In the event that the goal post is displaced, either deliberately or accidentally, prior to the puck crossing the normal positions of the goal posts, the referee may award a goal. In order to award a goal in this situation, the goal post must have been displaced by the actions of a defending player, the puck must have been shot (or the player must be in the act of shooting) at the goal prior to the goal post being displaced, and it must be determined that the puck would have entered the net between the normal position of the goal posts. The goal frame is considered to be displaced if either or both goal pegs are no longer in their respective holes in the ice, or the net has come completely off one or both pegs, prior to or as the puck enters the goal." This is not a reviewable call. Good goal Columbus.