Jr., the president of the National Hockey League, announced that protective helmets would become mandatory in the NHL. "The introduction of the helmet rule will be an additional safety factor", he said. The only exception to the rule are players—after signing a waiver form—who signed pro contracts prior to June 1, 1979. Essentially, this grandfather clause allowed hockey's veterans to choose whether or not they wanted to wear helmets but forced all new players to wear them. In 2013, visors in helmets became mandatory for players with 25 or less games of NHL experience. However, players who wore helmets without visors prior to the rule change may continue to wear them. Beginning the 2019–20 NHL season, a player on the ice whose helmet comes off must either pick it up and put it on properly, or skate to the bench (with a reasonable opportunity to complete his immediate play). Otherwise, a minor penalty shall be assessed. Intentionally removing an opponent's helmet during play became a roughing offense punishable with a minor penalty. Penalties A penalty is a punishment for infractions of the rules. A referee makes most penalty calls while the linesmen may call only obvious technical infractions such as too many men on the ice. In the NHL, the linesmen may also stop play due to player injury, and may report to the referees, during any stoppage in play, any circumstances pertaining to major, match, or misconduct penalties, abuse of officials (physical or otherwise), unsportsmanlike conduct, or double-minor penalties for high-sticking causing injury, that were not detected by the referees. During a penalty, the player who committed the infraction is sent to the penalty box. Small infractions are deemed minor penalties, and the player is kept off the ice for two minutes of gameplay. A larger infraction such as high-sticking that causes the victimized player to have a visible physical injury is deemed a double-minor, and the perpetrator is kept off the ice for four minutes. More dangerous infractions, such as fighting, are deemed major penalties and have a duration of five minutes. The penalized team cannot replace the player on the ice and is thus short-handed for the duration of the penalty. Normally, hockey teams have five skaters (plus the goaltender) on the ice. If a minor or major penalty is called, play becomes "five-on-four"—five skaters versus four skaters. This situation is called a power play for the