Different fields have different rules, but for the most part, BA certification is often asked for when the sniper is using a high-powered sniper rifle. Typically, snipers are shooting 450+ fps, and at velocities like that, the potential for injury is very real, especially when paired up with heavier BBs (usually 0.3g+ for sniping that hold their energy a lot longer in flight than lighter ones). Snipers need to understand minimum engagement distances, must be great marksmen, etc...
If you showed up with a sub-400 fps rifle, I don't thing anyone would care that you had a sniper or not. Certification is intended for high power rifles.