68.1 Illegal Substitution – An illegal substitution shall be deemed to have occurred when a player enters the game illegally from either the players’ bench (teammate not within the five (5) foot limit, refer to Rule 74 – Too Many Men on the Ice), from the penalty bench (penalty has not yet expired), when a major penalty is being served and the replacement player does not return to the ice from the penalty bench (see 68.2), or when a player illegally enters the game for the sole purpose of preventing an opposing player from scoring on a breakaway (see 68.3 and 68.4).
68.2 Bench Minor Penalty – When a player receives a major penalty and a misconduct or game misconduct penalty at the same time, or when an injured player receives a major penalty and is unable to serve the penalty himself, the penalized team shall place a substitute player on the penalty bench before the major penalty expires and no replacement for the penalized player shall be permitted to enter the game except from the penalty bench. Any violation of this provision shall be treated as an illegal substitution under this rule calling for a bench minor penalty.
68.3 Penalty Shot – If a player of the attacking side in possession of the puck shall be in such a position as to have no opposition between him and the opposing goalkeeper, and while in such position he shall be interfered with by a player of the opposing side who shall have illegally entered the game, the Referee shall impose a penalty shot against the side to which the offending player belongs.
68.4 Awarded Goal - If, when the opposing goalkeeper has been removed from the ice, a player of the side attacking the unattended goal is interfered with in the neutral or attacking zone by a player who shall have entered the game illegally, the Referee shall immediately award a goal to the non-offending team.
68.5 Disallowed Goal – If a penalized player returns to the ice from the penalty bench before his penalty has expired by his own error or the error of the Penalty Timekeeper, any goal scored by his own team while he (or his substitute) is illegally on the ice shall be disallowed but all penalties imposed on either team shall be served as regular penalties.
In summary, a team cannot score when one of their players has left the penalty bench early, either by his own error or the error of the Penalty Timekeeper. The goal must be disallowed and the player must return to serve his unexpired time (and an additional minor penalty if he left on his own).
If a player shall illegally enter the game from his own players’ bench or from the penalty bench, any goal scored by his own team while he is illegally on the ice shall be disallowed but all penalties imposed on either team shall be served as regular penalties.
68.6 Deliberate Illegal Substitution – see Rule 74 – Too Many Men on the Ice.