"A rushing defender is prohibited from forcibly hitting in the knee area or below a passer who has one or both feet on the ground, even if the initial contact is above the knee. It is not a foul if the defender is blocked (or fouled) into the passer and has no opportunity to avoid him.
Note 1: A defender cannot initiate a roll or lunge and forcibly hit the passer in the knee area or below, even if he is being contacted by another player.
Note 2: It is not a foul if the defender swipes, wraps, or grabs a passer in the knee area or below in an attempt to tackle him."