During most of the games I’ve watched there have probably been at least one illegal substitution call at each of them — or at minimum every other game. All this time it hasn’t been clear to me what exactly an illegal substitution really is. After a little digging around the web this is what I’ve come up with.
An illegal substitution is classified as a bench minor penalty. That means if the offending team has possession the call is made immediately — if not it is delayed, much like a roughing penalty — and the offending player is sent to the penalty box for two minutes. That much was pretty evident by watching the games.
The real question would ask what the criteria for calling an illegal substitution would be. It seems that an illegal substitution would be called mostly when teams on the offense pull the goalie and getting that extra player on — not that it would be the only situation but it’s a great example.
The official would call the penalty if the extra man crossed the line onto the field prior to the goalie crossing the line to the players box. A different example would be during the transition when a player in the box rushes to get out ahead of the defense on the opposing team — for a breakaway opportunity — before the defender he’s replacing gets back into the box — or at least on the table (more on that in the next few days).
That should give you a better idea of what’s going on when an official calls an illegal substitution. From what I’ve heard teams attempt to get away with this sort of thing as much as possible — although they may not admit it — and it usually only takes one call for this penalty to stop both teams from trying it.
As always, if you would like to contribute anything to this discussion, feel free to do so in the comments.