NHL Official Rules 2013-14 (PDF)

Rule 32 - Linesmen

32.1 Attire and Equipment: Black pants, "official sweaters," and a black helmet. Incidentally, there's nothing in the rules here that designates the referees wear the orange arm bands while the linesmen wear plain stripes, and I can't find anything anywhere else that talks about how the orange arm bands came into use. The linesmen are provided with the same equipment as referees for rules enforcement: whistle, tape measure, and an official stick-measuring gauge.

32.2 Face-offs: Excepting the starts of periods and the faceoffs directly after a goal, the linesmen conduct all other faceoffs. Now if only they were just as willing as referees to drop the puck without all the fuss.

32.3 General Duties: The linesmen enforce offsides and icing. They also enforce more technical situations "as noted in sections 32.4 and 33.5." I think 33.5 is a typo and meant to be 32.5; here's 33.5:

Penalties - The Official Scorer must help the Penalty Timekeeper with the numbers of the players on the ice, in the event a goalkeeper is assessed a penalty or a player is ejected from a game. He must also keep an eye on the players' benches during an altercation and record the numbers of any players who leave their respective players’ or penalty benches and in the order that they so leave.That rule totally has to do with the linesmen, yup yup yup.

32.4 Reporting to Referee: I said this last time in the post about referees:

[T]his stipulation means the referee will only consult with the linesmen on disputed goals. On the other hand, considering the four officials always gather after scrums to try and figure out penalties, the referees will also consult the linesmen when wanted to help figure out penalties. I say "when wanted" because I don't think a linesman can just go up to the referee and say "That guy tripped this guy" and expect the referee to impose a penalty.Contrast that analysis with this stipulation from the rulebook:

The Linesman shall give to the Referees his interpretation of any incident that may have taken place during the game.This rule makes it seem incumbent for the linesmen to tell the referees when they see something happen. This sentence creates all sorts of interpretive problems. Does the linesmen inform the referee of what happened regardless of what rules are being broken, or does the linesmen only inform the referee when certain rules are broken? I'm inclined to think the above cited sentence gives the linesmen broad scope to inform the referee of any incident regardless of whether the referee asks for it but so long as it pertains to rules enforcement. Whether the linesmen ever tell a referee in practice, "hey, I saw a guy trip someone and you missed it" is an entirely different story.

I say all this because the next paragraph says that the linesmen "may stop play and report" what he sees to the referee. Where the previous citation just says the linesmen can talk to the referee, the linesmen may also "stop play" when there are too many men on the ice; when items are thrown from the benches; when team personnel interfere with an official; when a player receives a new stick illegally after breaking or losing his original one (Rule 10.3); and when there is a high-sticking penalty severe enough to warrant a double-minor.

The next paragraph after that really doesn't clarify if the linesmen is allowed to inform the referee of incidents involving minor penalties. The linesmen "must" report during the next stoppage of play any information about major penalties, match penalties, misconducts, game misconducts, abuse of officials penalties, physical abuse of officials, and unsportsmanlike conduct penalties. So the linesmen isn't expressly forbidden from doing so, but does the listing of what the linesmen "must" report on limit him only to those specific penalties?

If a referee misses a call and the continuance of play results in a goal, the linesmen can tell the referee what he saw so long as it pertains to one of the above listed penalties (major, match, etc.). In that scenario, the goal will be disallowed and appropriate penalties assessed.

32.5 Stopping Play: The linesmen are also instructed to stop play when a premature goalie substitution has occurred; when a player is severely injured; when faceoff encroachment's occurred; when a hand pass violation either in the course of play or off a faceoff (the kind that results in a penalty) occurs; when the puck is played by a high stick; when spectators get involved in the play; when the puck leaves the playing area; "when a goal has been scored that has not been observed by the Referees"; when an ineligible player touches the puck; when a violation of Rule 53 Throwing Equipment should result in a penalty shot.

Remember that the linesmen are instructed to blow the whistle and stop play for these other infractions. So to recap: there's a general implication that the linesmen "shall" give the referees their take on "any incident" that took place. Who is ultimately responsible for making sure information is relayed is anyone's guess: Are the linesmen able to just tell the referee "hey you missed something" and expect the referee to call it? Or do the linesmen have to wait for the referee to ask them before they can give their input? Apart from the general implication, the linesmen "may stop play and report" what he sees in relation to another class of penalties. Then the linesmen "must report" (but not "stop play") information relating to another set of penalties. Finally, the linesmen "must" or "shall" stop play for yet another class of infractions. You following me?

The other stipulation added to a lot of the situations where the linesmen can stop play is the provision of "when this has gone undetected by the referee." If the rulebook is going to give the linesmen the power to stop play anyway, I fail to see the purpose of waiting for the referees to "not detect" that some infraction has occurred. Just let the linesmen stop play immediately instead of wasting the second or two it takes to see if the referee is going to call it first.

32.6 Unable to Continue: If the linesmen cannot discharge his duties, the referees have the power to appoint someone else to do so if the referees themselves decide to use this power of appointment -or- if either of the competing teams "require" it of the referee. If there's no replacement linesman available, the two referees will assist the lone linesmen in executing his duties "while still retaining their ability to assess penalties when deemed appropriate."

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In practice, the linesmen pretty much seem to say nothing if a referee misses a minor penalty, even if the missed call leads directly to a goal. Watching enough hockey games gives you a pretty good sense of what the linesmen can and can't call and also what the referee can and can't call. How much discretion the linesmen have in terms of when and what to tell the referee doesn't seem to be very clear from this section of the rulebook, but who knows what we'll run into at later points.

Also in practice, the rulebook doesn't spell out explicitly which set of officials are the ones who should break up a scrum or fight, but watching a number of games, I notice more often the linesmen streaking down the ice to break up fights and the referees just standing off to the side. Whether that's just convention or the referees aren't needed and the linesmen usually can handle the job of restoring order is something not explained in the official rules.

Due up next are the Official Scorer, Game Timekeeper, and Penalty Timekeeper.