The NFL reacted to litigation from current and future players regarding concussions by enacting a rule to outlaw the use of the crown of the helmet by offensive or defensive players in the open field.
Ian Rapoport of the NFL Network reports that the rule passed by a "wide margin." More details may arise as to who supported and who opposed the rule change.
Yet another effort by the NFL to make an unsafe game more safe. It will be interesting to see how this rule plays out in real games. Many players use their head as a battering ram and that type of action is difficult to learn after playing the game for so long.