Spot throw-in
 

Following a TO the ball is bounced to A1 for a spot throw-in on the backcourt (endline). Before the ball is caught by A1 he runs inbounds & A2 simultaneously replaces him & catches the bounced ball. What do we have?

I know the thrower (A1) cannot be replaced on a spot throw-in once the ball is at his dispossal. But isn't dispossal defined as the ball being caught by the thrower when bounced to him?

Help me out, thanks!

Blow the whistle, get the ball back, re-administer the throw-in.

Yes, this is why you blow the whistle and readminister the throw-in.

Why? What did Team A do that was illegal/needing referee's intervention?

Just asking...

I'd like to add my ??? to the Juggler's question.

Key words are "before A1 catches ball". Ball not yet at disposal. Nothing wrong here.

MS game 10 years ago in upstate NY. Ball goes out of bounds under team A basket. I hand ball to A1 for throwin. Ball at his disposal now. Before A1 throws-in, A2 nonchalantly walks toward A1 and says he will take throw-in. Defender backs off A2. A1 throws ball to A2 who moves toward end-line then quickly cuts to basket and scores. Couldn't do anything about that because A1 already had ball at his disposal. Seemed to me to be deceptive and unsportmanlike but is there anything you would have done differently?

I've seen that play before, in a Freshman girls game. Worked just as well; wouldn't work at a higher level, though.