Here are the 2001 rules.
I will check later to see if the 2006 rules are different.
The 2006 rules are in fact different.Here is Rule 8, Section 2, Article 5:
It is pass interference by either team when any player's movement beyond the line of scrimmage significantly hinders the progress of an eligible player or such player's opportunity to catch the ball. Offensive pass-interference rules apply from the time the ball is snapped until the ball is touched. Defensive pass-interference rules apply from the time the ball is thrown until the ball is touched.
Actions that constitute defensive pass interference include but are not limited to:
(a) Contact by a defender who is not playing the ball, and such contact restricts the receiver's opportunity to make the catch.
(b) Playing through the back of a receiver in an attempt to make a play on the ball.
[c] Grabbing a receiver's arm(s) in such a manner that restricts his opportunity to catch a pass.
(d) Extending an arm across the body of a receiver thus restricting his ability to catch a pass, regardless of whether the defender is playing the ball.
(e) Cutting off the path of a receiver by making contact with him without playing the ball.
(f) Hooking a receiver in an attempt to get to the ball in such a manner that it causes the receiver's body to turn prior to the ball arriving.
Actions that do not constitute pass interference include but are not limited to:
(a) Incidental contact by a defender's hands, arms, or body when both players are competing for the ball, or neither player is looking for the ball. If there is any question whether contact is incidental, the ruling shall be no interference.
(b) Inadvertent tangling of feet when both players are playing the ball or neither player is playing the ball.
[c] Contact that would normally be considered pass interference, but the pass is clearly uncatchable by the involved parties.
(d) Laying a hand on a receiver that does not restrict the receiver in an attempt to make a play on the ball.
(e) Contact by a defender who has gained position on a receiver in an attempt to catch the ball.
Actions that constitute offensive pass interference include but are not limited to:
(a) Blocking downfield by an offensive player prior to the ball being touched.
(b) Initiating contact with a defender by shoving or pushing off, thus creating a separation, in an attempt to catch a pass.
[c] Driving through a defender who has established a position on the field.
Actions that do not constitute offensive pass interference include but are not limited to:
(a) Incidental contact by a receiver's hands, arms, or body when both players are competing for the ball, or neither player is looking for the ball.
(b) Inadvertent touching of feet when both players are playing the ball or neither player is playing the ball.
[c] Contact that would normally be considered pass interference, but the ball is clearly uncatchable by involved parties.