runner foot position in LL

[parrothead]

Because in LL you cant lead off, I have often had my runners take the fastpitch softball approach to running, sort of like getting ready to run a race, left foot on the bag, right foot back/side with the idea that the right foot starts forward right as the ball is reaching the batter and you can actually start moving while still attached to bag.

Anyhow in game last week, I think my runner at first base had his right foot in foul territory, left foot on the bag and umpire instructed that both feet must be in play and it was no biggie, didnt say anything, but I got to thinking after the game, when you think at 3B, all runners take their lead in foul territory, so I was a little puzzled, but just curious what the rule is.