NFL to clamp down on clutching and grabbing
"'I don't really understand what we're trying to do' Belichick said. Belichick said that in many of the examples on a demonstration film shown to coaches, it was unclear to him whether a violation occurred. "

Now THERE'S the best explanation I can find of the "genius" of Bill Belichick. Just have your secondary pull the other team's receivers down. After a while, everyone forgets it's illegal.