From the NFL Rulebook:
ILLEGAL CONTACT BEYOND FIVE-YARD ZONE
Beyond the five-yard zone, if the player who receives the snap remains in the pocket
with the ball, a defender may use his hands or arms only to defend or protect
himself against impending contact caused by a receiver. If the receiver attempts
to evade the defender, the defender cannot chuck him, or extend an arm(s) to cut
off or hook him, causing contact that redirects, restricts, or impedes the
receiver in any way.
I’m not a fan of this rule, for a variety of reasons. And I don’t care for all the whining of Jim Harbaugh, Crabtree, et. al.
But I have no respect for officials that swallow their whistles late in games.