Here you go...from page 22 of rule book version 2017.2.
6.4 Stage Boundaries
Stage boundaries must be defined at each stage, located no more than 10 yards back from the furthest up range shooting position. Rope, tape, cones, flags, etc. must physically indicate these boundaries.
Yeah, but it says nothing about staying outside the stage boundaries until the range is called clear. The stage boundaries are just the "no airgunning" zone.