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; it's prohibited for women. Before that, body-checking was only allowed in the defending zone in international hockey 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. 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. 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.