The NFL removed the exceptions that made chop blocks legal and instead passed a rule change that will make all blocks below the waist a 15-yard penalty if a player is already engaged with another player high.
While most chop blocks were already illegal, the rule change removes a few loopholes that allowed the blocks in certain cases. Previously, there were a few exceptions on run plays only that allowed chop blocks in certain cases that mostly had to do with player alignments.
In February 2015, NFL executive vice president of football operations Troy Vincent appealed for a ban of all chop blocks in the name of player safety.
FINALLY! No Chop blocks! @NFL got this 1 right! Now see about getting to the bottom of that mysterious catch rule! lol— Patrick Peterson /P2 (@RealPeterson21) March 22, 2016
"The chop block has been banned from both the high school and college game," Vincent wrote. "We have a generation of players coming to the NFL who never used the chop block, yet they may be expected to initiate this technique that could result in a career-ending injury. We strongly need to consider removing this technique from the game."
The sole note that allows for a player to be hit high and low by blockers is if a slip or attempt to escape from an opponent results in incidental contact.