Which of these sports forbids anyone from playing left handed?

Polo is a team sport played on horseback. The objective is to score goals against an opposing team. Players score by driving a small white plastic or wooden ball into the opposing team's goal using a long-handled mallet. The traditional sport of polo is played on a grass field up to 300 by 160 yards (270 by 150 m). Each polo team consists of four riders and their mounts.

The banning of left-handed playing in a game of polo is for safety reasons in order to avoid the likelihood of a head-on collision between players. As a left-handed player and a right-handed player head for the ball, they would not pass each other as they do in right-hand only games.

Left-handed people are not banned from the game; they must play right-handed. There are some professional left-handed polo players who play right-handed. The use of the left hand or the mallet was banned in the 1930s. The rule was relaxed after World War II when there was a lack of players, but the rules were re-introduced in 1974.