NFL owners tabled a proposed change to the rules governing blocks below the waist earlier this year, but they voted to approve it on on Wednesday.
The change expands the area where blocks by offensive and defensive players are prohibited. Such blocks are now against the rules when they occur within the tight end box.
The tight end box is defined as five yards on either side of the line of scrimmage and two yards outside either tackle position. All contact below the waist outside that box is now barred except for when it involves a runner or player trying to catch a forward or backward pass. That would include a defensive player taking out the legs of a pulling lineman in addition to any blocks made by offensive players.
A penalty for an illegal block below the waist will cost a team 15 yards.