Throw-in question; when can the thrower legally touch the ball again?
 

A1 is the designated spot thrower. A1 inbounds the ball to A2. Does A1 need to have one foot touching the floor inbounds or two before A1 can legally touch the ball again?
I reviewed rules 7 & 9 but could not find an answer.

Look at rule 4, player location. A1 must be inbounds, which is defined there.

4.35.2
 

Thank you mbyron


4.35.2 SITUATION:
Thrower A1 inbounds the ball to A2. A2 immediately throws
the ball back to A1. When A1 touches the pass, he/she has: (a) both feet touching
inbounds; (b) one foot touching inbounds and one out of bounds; or (c) one
foot touching inbounds and the other not touching the floor. RULING: The ball
remains live in (a) and (c), but A1 has caused the ball to be out of bounds in (b).
(4-4-4)

This also appears in the 2010-11 NFHS Basketball Preseason Guide. There is an article on page 8 entitled Location, Location, Location and this situation is Play 1.
The ruling is very clear and states that the action stated in part (c) above is "perfectly legal. No violation and play continues. The plane of the boundary has no bearing on the location of A1, who is considered to be inbounds because neither foot is out of bounds. (4-35-1a, 4.35.2)"