Batter advancing after a walk (BB)

Question
After receiving a walk, can the batter keeping running to second base, even though the pitcher has the ball inside of the pitching circle.
Recent Game: Runner on third base. Batter receives a walk. Batter runs to first base and keeps on running until reaching second base. Coach says the pitcher had the ball inside the pitching circle, and the runner can not advance. By rounding first base, the batter should have been called out for leading off.
Umpire says the batter did not stop at first base and continuing to second base was legal.  Who is right?

Answer
Hi Frank,

The fact that the pitcher has the ball in the circle does not prevent a b-r from advancing on a walk, it simply makes the LBR (look back rule) in effect.  The b-r may round 1st, stop once (if they wish) and immediately advance or retreat.

The umpire is correct and the coach does not understand the LBR.

Mark