Raida357 - welcome to the forum. Hopefully you'll learn a lot while you're here. (Some of it may actually be basketball-related.
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What level did this happen?
The reason I ask is that at lower levels, such as grade school, I would be more apt to believe it was simple confusion by the young players. Therefore, I would blow my whistle, tell them they need to do it the right way, and give them back the ball for the throw-in. If they continue to do it, I would call the violation.
At the higher levels (HS and beyond), I would treat it a little differently. At that level the players should be well aware of the rules, so as soon as A2 starts dribbling up court, I would call the violation.