[AtlUmpSteve]

Mike has actually answered you; but, I find that sometimes it helps if someone else rephrases an answer.

If a batter-runner interferes with the possible catch of a throw in fair territory by a fielder in position to make that catch, that is a violation of the 3foot running lane rule. The interference can be by contacting the ball or screening the fielder, either intentionally or inadvertantly; but the interference, if it occurs, must happen over fair territory, regardless how much of the BR may be in foul territory.

The exception to this rule in ASA is if the play is coming from foul territory to begin with, and the fielder chooses the orange (foul territory) base when a double base exists, then the batter-runner is given an equivalent 3 foot running lane in fair territory, since she may then use the white (fair) first base. In that case, the runner actually has a 6 foot running, 3 feet on either side of the fair line. To my knowledge, NFHS does not have an equivalent exception, and it does not apply in NCAA, which doesn't use a double base.

Does that rewording make it clearer?