ASA vs NFHS Pitching Rules
 

In ASA the start of the pitch is when the hands separate. In FED they go one better and say the pitch starts when the hands separate or when the pitcher makes any motion that is part of the windup. What implications are there due to these rule differences? Are there things a pitcher can do in ASA while the pitcher is in her windup but the hands haven't separated yet that they can't do in FED?

A pitcher is on the pitching plate, takes the signal and then brings her hands together and pauses. She then does a 'false start' of moving only six to ten inches as if she were going into her wind up. Shen then stops and (a) steps off pithcing plate, or (b) restarts her windup and delivers the pitch.

What's the call in ASA vs Fed?

In ASA nothing. In FED Illegal pitch.

In both ASA and FED
 

In both ASA and FED the rulebooks state that "The pitcher may use any windup desired provided no motion to pitch is made without immediately delivering the ball to the batter". However, as I stated before in ASA and FED the start of the pitch is defined differently. Therefore, the above rule should be interpreted to mean that once the pitch has started, no motion to pitch can be made without immediately delivering the ball to the batter. So in ASA the pitcher can stop her windup before she separates her hands because the pitch has not begun yet, but in FED she can not. Correct?

That's my understanding, too. In "real life", if a pitcher does a quick start of her motion and then stops, should the umpire just call time to allow everyone to reset... and realistically do you do differently for ASA vs FED?

Probably Not
 

Most pitchers aren't going to bring the ball to the side and stop. It is normally part of their windup and they will continue with the motion. However, it could happen and in an ASA game, it is legal and should be allowed. In FED, it's illegal.

The motion being discussed here is the motion prior to the hands separating for the back swing. In Fed, the pitcher cannot NOT deliver the pitch once she starts her windup, but it does not say she cannot stop moving.

Actually, it does
 

Per FED, The picther may use any windup desired provided:

a. no motion to pitch is made without immediately delivering the ball to the batter. ===> So once the motion starts if they stop then they have not immediately delivered the ball to the batter.

The same is true for ASA, but the point the pitch starts is different. In ASA the pitch starts once the hands separate, so any stop before that point is legal. After that, it's an illegal pitch.

You are overinterpreting what this means. Would you call this an IP in NFHS? Pitcher brings hand together and pulls them (together) back to her body. She takes her step forward while separating the hands and beginning the windmill. This is a common mechanic, yet the hands come together, the motion of the windup (Fed definition) begins, and the hands stop before they separate.

And, in ASA, the pitcher cannot stop the forward motion after the hands separate.

In neither code can the pitcher stop the pitch. But we were discussing stopping the motion of the hands before they separate.