Here's the rule: Rule 8, Section 4, Article 3:
ILLEGAL CONTACT BEYOND FIVE-YARD ZONE
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 initiate contact that redirects, restricts, or impedes the receiver in any way.
Verdict: Gronk was held while Tom Brady no longer held the ball in the pocket. Therefore, illegal contact cannot be called.
What about defensive holding? That's a hold if I've ever seen one, right?
Here's the rule: Rule 8, Section 4, Article 6:
Defensive Holding. It is defensive holding if a player grasps an eligible offensive player (or his jersey) with his hands, or extends an arm or arms to cut off or encircle him.
Fits the fill, right? In every way, shape, and form?
Rule 8, Section 4, Article 7, however rains on the parade:
End of Restrictions.
If the quarterback or the receiver of the snap demonstrates no further intention to pass the ball (i.e., hands off or pitches the ball to another player, throws a forward or backward pass, loses possession of the ball by a muff that touches the ground or a fumble, or if he is tackled) the restrictions on the defensive team prohibiting illegal contact, an illegal cut block, or defensive holding against an offensive receiver will end.
Which means that once the quarterback throws the ball, the restrictions stopping defensive holding ends.
Which leads to pass interference:
Pass interference is called if a player's ability to catch the ball is impeded while a yard or more beyond the line of scrimmage. Defensive pass interference applies from when the ball is thrown until the ball is touched be a person or the ground (important!).
(a) Contact by a player who is not playing the ball that restricts the opponent’s opportunity to make the catch.
© Grabbing an opponent’s arm(s) in such a manner that restricts his opportunity to catch a pass.
(d) Extending an arm across the body of an opponent, thus restricting his ability to catch a pass, and regardless of whether the player committing such act is playing the ball.
(e) Cutting off the path of an opponent by making contact with him, without playing the ball.
© Contact that would normally be considered pass interference, but the pass is clearly uncatchable by the involved players.
The flag was picked up because the pass was deemed uncatchable.
credit to the Patriots blog : http://www.patspulpi...-the-final-play