I got in a minor pissing match with a young ref at "my" field (you know, the one you've been playing at for 10+ years) about just this issue last fall... Bear in mind they have an established surrender rule.
I came down the side of the field to flank the enemy fort in a friendly recreational "storm the castle" game where the objective is to reach and physically touch the fort. I found a guy was locking down a kitty corner TP bunker on the side of the fort near one of the refs, occasionally shooting across the front of of the fort to the other side of the field - I discovered this by walking sneakily in the back of the bunker to finding him about six feet in front of me starting to shoot.
I said "surrender" loudly enough for him and the ref to hear me; I was too close to shoot him safely and he wasn't wearing a podpack for me to tag. The kid turned around slowly, then the ref yelled out "there's no surrender" at which point the kid shrugged and lit me up. Needless to say I was bruised and pissed, and probably should have bunkered him and shot him in his stupid head, but it's just as much the referees fault as I see it.
Anyhow I've never been to a recball game at any field without a surrender rule, at least not in the last decade or so. I've seen 10ft, 15ft and 20ft rules... Generally it covers getting the drop on someone (sneaking up up somewhere in the rear 180 to 240 degrees which are not visible to them) and rather than shooting them from close range you yell "surrender" or tag them with your barrel tip.