The NHL has modified enforcement of the jersey tuck rule to avoid confusion when a player's jersey tucks into his pads during the course of play, according to Elliotte Friedman of CBC.
In the event that a player's jersey tucks into his equipment during the course of play, he will not be given a warning or penalty for the offense as long as the jersey was untucked at the beginning of the shift.
The NHL decided to strictly enforce this policy beginning in the 2013-14 season at the behest of the league's general managers. In the event that a player tucks his jersey into his pants, he will be given a warning followed by a two-minute minor for delay of game. If the player is caught with his jersey intentionally tucked in three instances, he will be given a misconduct followed by a game misconduct.
This clarification was made to ease concerns about accidental tucking and is meant to "deliberately flout this crackdown," according to Friedman.