American Football IFAF Approved Ruling 9-1-6:VI, IX

VI. Defensive end B88 blocks below the waist against tackle A75 one yard beyond the line of scrimmage. The block is^´ at the opponent’s side. RULING: Foul for illegal block below the waist. The block takes place within the 10-yard belt, but to be legal, it must be directed from the front.  [Cited by 9-1-6-b-1]

IX. First and 10 at the A-40. A12 takes the snap and starts on a sweep to his/her right. Guard A66 pulls and leads the play. As the play develops, linebacker B55 blocks A66 from the front at the thigh at the A-44. A12 is driven out of bounds at the A-48. RULING: No foul. B55’s block below the waist is legal because it occurs fewer than five yards beyond the neutral zone and is directed from the front. ^´ [Cited by 9-1-6-b-1]