[ Working off of intent, huh? That's an interesting way for this to work, and that could make this trickier too, because now his question is less about intent and more... ]

If that's the case, then what about if we're not aiming at the barrier itself...

[ He looks at a tree that's a little distance past it, closing one eye as he tries to take good aim. ]

But aiming at something on the other side of it?

[ And with that question ask he lobs the rock as hard as he can with the full intention of hitting the tree.

It's not a person, so who is to say if it'll work? Might be nice to know beforehand before they're trying to ward off an attack, and people are firing arrows at them. ]