[OKREF]

Originally Posted by APG

A.R. 89. A1 tries a pump fake and defender B1, who is in legal guarding
position:

1. Jumps forward into the air and A1 then jumps forward and makes contact with B1 in the air; or

2. Jumps straight up in the air and A1 then jumps forward and makes contact with B1 in the air.

RULING 1: Even though B1 established legal guarding position on the floor, his jump forward and toward A1 is not a legal attempt to maintain legal guarding position so that any non-incidental contact with A1 is a personal foul on B1. However, if B1’s jump forward is in a direction that he clearly would not have made contact with the shooter, and the shooter moves sideways to cause the contact, B1 has not committed a personal foul. (Rule 4-17.6.e)

2: B1 has again established initial legal guarding position and his jump into the air is a legal attempt to maintain legal guarding position as long as the jump is within B1’s own vertical plane. Any subsequent contact by A1 jumping forward and into B1 is either a personal foul on A1 or incidental contact. (Rule 4-17.6.e)

Bolded portion is the new part of the case book play

I love this addendum. I wish NFHS would adopt this.