9-13-2. . . A player may extend arm(s) or elbow(s) to hold the ball under the chin or against the body.
So, A1 holds the ball as described, above, and B2, guarding A2 runs into A1's elbow.
What do we have?
(I've seen this, numerous times, and even with severe contact to the head of B2.) What judgement factors do you use regarding such contact?