When is the B-R "out of the batter's box"?

[umpman1]

I think my confusion comes from a thread posted two years ago.

Foul Ball? or?
Any rule set. LH or RH batter, swinging or bunting. Ball hits plate and bounds up in air. B-R starts for 1B. B-R is mostly out of box, but trail foot is still in box or on line when ball comes down and hits B-R.

Foul ball? Or Interference?

WMB


A reply by CecilOne:

I thought we resolved the "in or out" issue as either foot in the box counted as in the box. That would mean foul ball.



And another by IRISHMAFIA:

Speaking ASA

Where does it hit the BR? If on part of the body still in the box, foul ball. If on part of the body out of the box, INT.


And this summation by WestMichBlue

Both ASA and NFHS definitions of Foul ball say "ball hits batter." Doesn't say where! It does say where the batter is - "in the box." Is not the batter still in the box when one foot is still in or on the line?

Either way, I think that FOUL is the "safe" call. Kill the play, and it diffuses everything immediately!

WMB


Now it seems that the early consensus in this thread has it just the opposite or at least some of both rulings.
What I really want to know is what is the definitive answer to WMB's original question of "Foul or Interference"? If the B-R contacts the ball in front of the plate in fair territory with one foot on the ground outside of the batters box and one foot on the ground inside the batters box, which way do you call it?