At the first tournament in 1920, there were many differences from the modern game: games were played outdoors on natural ice, forward passes were not allowed,
[13] the rink (which had been intended to be used only for figure skating) was 56 m × 18 m (165 ft × 58.5 ft)
[5] and two 20-minute periods were played.
[12] Each team had seven players on the ice, the extra position being the
rover.
[6] Following the tournament, the IIHF held a congress and decided to adopt the Canadian rules—six men per side and three periods of play.
[13]
The tournaments follow the rules used by the IIHF. At the 1969 IIHF Congress, officials voted to allow
body-checking in all three zones in a
rink similar to the NHL. Before that, body-checking was only allowed in the
defending zone in international hockey.
[139] Several other rule changes were implemented in the early 1970s: players were required to wear
helmets starting in 1970, and
goaltender masks became mandatory in 1972.
[6] In 1992, the IIHF switched to using a playoff system to determine medalists and decided that tie games in the medal round would be decided in a
shootout.
[140] In 1998, the IIHF passed a rule that allowed two-line
passes. Before then, the
neutral zone trap had slowed the game down and reduced scoring.
[141]
The current IIHF rules differ slightly from the
rules used in the NHL.
[142] One difference between NHL and IIHF rules is standard rink dimensions: the NHL rink is narrower, measuring 61 m × 26 m (200 ft × 85 ft), instead of the international size of 61 m × 30 m (200 ft × 98.5 ft)
[143] The larger international size allows for a faster and less physical style of play.
[144][145] Another rule difference between the NHL and the IIHF rules concerns how
icing is called. In the NHL, a
linesman stops play due to icing if a defending player (other than the goaltender) touches the puck before an attacking player is able to,
[146] in contrast to the IIHF rules in which play is stopped the moment the puck crosses the goal line.
[146] The NHL and IIHF also differ in penalty rules. The NHL calls five-minute major penalties for more dangerous infractions of the rules, such as fighting, in addition to the
minor and double minor penalties called in IIHF games.
[147] This is in contrast to the IIHF rule, by which players who fight are ejected from the game.
[148] Beginning with the
2005–06 season, the NHL instituted several new rules. Some were already used by the IIHF, such as the shootout and the two-line pass.
[149] Others were not picked up by the IIHF, such as those requiring smaller
goaltender equipment and the addition of the
goaltender trapezoid to the rink.
[150] However, the IIHF did agree to follow the NHL's league's zero-tolerance policy on obstruction and required referees to call more
hooking, holding, and interference penalties.
[151][152]