Law 3 of the Laws of the Game governs substitutions in the (3) Substitution Procedure section. A player can only be substituted during a halt in play and with the referee's approval. The substitution may be made by any member of the match committee provided that a substitute is appointed for each player who is replaced. In addition, Law 12 states that if a player has not returned to his/her seat between moves, the president of the league can require him/her to be replaced. The replacement player should be chosen from among the remaining players. If no replacement player can be found, then the game continues with fewer players. A player who has been substituted away cannot return to the field of play until the substitution has taken place. This includes if the player returns during injury time or in stoppage time. However, if a player who has been substituted goes back on injury ground, this would be considered returning to the field of play. The only exception to this rule is if a player is injured and requires attention from a medical staff member, he/she can be substituted at any time before that player receives treatment. For example, let's say player B hits with enough force to break player A's leg. Player A goes to the sideline and does not return.