obs on throwback

[ggk]

2006 Legion Guide
Rule #22, Approved Ruling 2
.........If the defensive player blocks the base (plate) or base line clearly without the ball, or is not in the immediate act of catching the ball, obstruction shall be called.

i think the intent of this rule is pretty much the same on all levels. it allows the fielder to momentarily block the base or plate while he is about to receive a throw.