There are a ton of unclear rules in the NHL rulebook, but the most hard to suss out one may be the concept of interference.
Spanning two and a half pages in the rulebook itself, interference is the only rule that needs a full page and a half of definition and setup before getting into the actual minor and major calls. I'd quote the full thing here, but it won't help anything because several key concepts are still left unclear.
To be clear, the last thing this piece is meant to do is call out the referee who made the call itself. Yes, there is a tremendous problem in the conception of NHL playoff refereeing "only calling the things that matter," and we'll get into that tomorrow. But in isolation, with one back angle and in real time, this call is understandable, though arguable via the letter of the law.
So let's start with the two parts of the rule that are most in play here, the idea of a player's right to his own ice and the definition of a pick.
This is from 56.1, the defining of body position, which is earlier defined as: "Body position shall be determined as the player skating in front of or beside his opponent, traveling in the same direction."
So, what is the same direction and what is in front of his opponent? After all, Antoine Roussel is in "front" of Jay Bouwmeester the entire play and actually cutting slightly away from him, as shown by this series of screenshots.
Roussel is also traveling toward where the puck is going from his starting point and not lateral to it (because if he traveled forward, he would be offside, and a player is not required to move to allow an opponent to proceed and is is also allowed to lengthen his opponents path).
But he is traveling at a 45-ish degree angle to Bouwmeester, who is cutting down the ice and across toward Ales Hemsky, and it's unclear in the rule if this is a true lateral play from him. He has well established body position in front of Bouwmeester and does not deviate from it. He also sees Bouwmeeester coming and braces himself, but who is moving into whose path? Well, they both are - neither deviates from their initial trajectory, and it's two paths converging rather than someone making a big move to cut someone off.
Maybe the definition of a pick will help out
So this doesn't help much either. There are two parts of this rule that are unclear in this situation - what does it mean to "move into an opponent's path without initially having body position" when you have two players coming from different starting points converging on the same spot, and what would make a player unaware of an impending check?
Now, some cases of that may be clear - a player who comes up an opponent's back for a body check, or a player who has his head clearly turned away from the oncoming opponent the entire play would suffice. But in this case, while Bouwmeester does not appear to register Roussel's presence, he swings around to face him and his head goes right by him on his initial turn from backwards to forward. He should have seen him (and had every opportunity to as Roussel was facing forward the entire play).
The rule is unclear on what, if anything, should happen when a player has the opportunity to see the impending collision but doesn't. Some rules lay this out - boarding comes to mind - but that is a very gray area here.
In fact, this is why a whole bunch of things off a faceoff play are let stand even though in basketball it would be considered a great pick. Players are assumed to be able to see the "rotation pick" in front of them and therefore avoid the collision by going around. Actually running into a guy is considered to be the fault of the defending player rather than the one on offense.
Now, given the screenshots above, it's clear Roussel lowered his shoulder and braced for the collision. But this leads to an additional complication to this rule - say Roussel had his eyes locked on Hemsky and the collision occurred the same way, except Roussel got knocked into the zone in an offside position. Technically, then Bouwmeester would have been guilty of interference per Rule 56.2:
A minor penalty shall be imposed on a player who shall cause an opponent who is not in possession of the puck to be forced off-side,causing a stoppage in play. If this action causes a delayed off-side (and not necessarily a stoppage in play), then the application of a penalty for interference is subject to the judgment of the Referee.
Now, they would never ever call that. Not because Roussel would have been the fouled party, but because I'm not sure I've ever actually seen that part of 56.2 called as many of those collisions are deemed "two players with the right to the same ice converging on a location." A player recognizing the impending collision and bracing for it should not change that logic.
But that demonstrates the the difficultly in applying the letter of the interference law - the referees clearly don't in most or all cases except when they feel some level of result barrier has been breached. While that is appropriate for a handful of calls that are based on nothing other than result - boarding, delay of game and high sticking come to mind immediately - it is not appropriate for the vast majority of calls that occur and are called on a scale.
So was this a penalty? Like I said, I understand the call in a vacuum because of the problems with how the rule is written and the way this particular situation developed. Bouwmeester was clearly prevented from continuing on a path to Hemsky, but Roussel may have had every right to continue on his previous path and brace himself for contact by letter of the law (heck, you can argue by being aware of the collision and bracing himself himself he kept Bouwmeester from taking a penalty). It all depends on how you interpret things such as what it means to be in front of another player, and whose responsibility is it for a player looking right at, but not registering, an opponent in his forward path.
From my perspective, the real problem with the call lies in the context of previous non-calls, and that is a subject for another article.