Question about NHL rule?

The rule used to be if he swung and hit the puck first there was no penalty even if he tripped him; the theory was that he has already knocked the puck away so he is not taking away a scoring chance, or affecting the play. Now it is supposed to be a tripping penalty if he trips the player, regardless of whether or not he hits the puck first. The refs don't usually call the rule right though, and still go by the old rule.