Jump Stop

[twref]

Jump Stops confuse me.

Play #1-A1 is dribbling down the floor-stops the dribble and, allthough attempting to perform a jump stop, in reality has the left foot hit the ground well before the right foot. I assume the left foot is now the pivot foot and the player can pass or shoot the ball. Can I also assume there is no violation if the player jumps off his left foot and releases the ball before the left (pivot) foot returns to the ground?

Play #2-A1 is dribbling the ball down the floor and, when ending the dribble, performs a good jump stop. Can either of the feet be considereded the pivot foot?