I couldn't find anything in the official rulebook specifically citing "over the back" as cause for a foul. However, I found this:
Section 6, Art. 5: It shall be illegal to extend one’s arms fully or partially, other than vertically, so that the freedom of movement of an opponent is hindered when contact with the extended arms occurs
So essentially "over the back" might be some combination of this "freedom of movement" and/or a push? The rules can sometimes appear tricky. I also found this:
Section 6, Art. 2: It shall be legal for a defender to accidentally hit the hand of a ball- handler when reaching to block or slap the ball when there is player control with that player’s hand in contact with the ball and when that player is:
- A dribbler;
- Attempting a try for field goal; or
- Holding the ball
Really confused by what this means because it seems to completely negate fouls when trying to block a shot and a player hits an opponent on the hand. Maybe I'm misunderstanding this completely and if that's the case I could use an explanation.
http://www.ncaapublications.com/productdownloads/WBR19_20180906.pdf