The rule bans "blind-side" hits to an opponent's head and allows the league to review questionable hits and dole out "supplementary discipline," such as suspensions or fines.
The NHL said the rule will go into effect beginning with games Thursday. The measure will be in effect through the 2010 playoffs and the NHL/NHLPA Competition Committee will develop a more permanent measure this summer.
NHL owners voted earlier this week to ban "a lateral, back-pressure or blind-side hit to an opponent where the head is targeted and/or the principal point of contact." The NHL Board of Governors and the players' union board gave their blessing to the proposed rule.
"We believe this is the right thing to do for the game and for the safety of our players," Commissioner Gary Bettman said in a release. "The elimination of these types of hits should significantly reduce the number of injuries, including concussions, without adversely affecting the level of physicality in the game."