Just a quick question on whether or not this play is travelling.

Someone receives the ball (has not used his dribble yet), and jumps up (like to shoot), sees that he's going to be blocked and then puts the ball to the floor to initiate a dribble.

Isn't this travelling?

Yes.

You cannot move your pivot foot to start a dribble.

Peace

I don't think is traveling yet. On this case the pivot foot has not been stablish. If he jump and land with both feet then he can't not move either of them if he do it will be traveling.

check rule book 4-44-1 and 4-44-2a and b

Wrong. You're taking rules that apply only to a player <b>catching</b> the ball, and then trying to also apply those rules to the situation where a player is <b>shooting</b> the ball. Jumping to shoot is a completely different circumstance and is governed by a different rule. The applicable rule on a shot is R4-44-3(b) and casebook play 4.44.3SitB is almost the exact same play.

Nope, I'm afraid you're wrong. "A player who catches the ball with both feet on the floor, may pivot, using either foot. When one foot is lifted, the other is the pivot foot." Whether he lifts them simultaneously or not, once he lifts a foot, a pivot is established. This is traveling.

4.44.3 SITUATION B: A1 receives the ball with both feet off the floor and he/she lands simultaneously on both feet without establishing a pivot foot. A1 then jumps off both feet in an attempt to try for goal, but realizing the shot may be blocked, A1 drops the ball to the floor and dribbles.

RULING: A1 has traveled as one foot must be considered to be the pivot and must be on the floor when the ball is released to start a dribble. The fact that no pivot foot had been established does not alter this ruling.