Question: 1931–32 Boston Bruins season, in the course of playing a 0–0 tie against the New York Americans on 3 January 1932, the Bruins shot the puck the length of the ice 87 times to relieve pressure on their goal, to stop this becoming a regular tactic, which rule, an infraction in the sport of ice hockey, was introduced into the NHL later in the decade? 
Sentence (from "Icing (ice hockey)"): However, it is "not" icing if the puck is shot from behind the halfway line "into the goal"; if the puck crosses the goal line completely, the goal is counted.
Relevant evidence: No