Board Thread:Speculation House/@comment-4830106-20131108040231/@comment-24198837-20140323174800

I hope that Semblance follows an Eragon-like way of dealing with things. As in, you can only affect things through your semblance if you could in reality, and it takes the same toll on your energy. If Pyrrha magnitizes a sword away from her, it would take the same strength as actually grabbing the sword and re-directing it. However, because of aura, everyone is super strong, which is why Semblance use has had no apparent affect on any of the characters thus far (Except Weiss when she made the path for Ruby to drag the Nevermore up the cliff, but no normal human without aura could expend the energy to do that).

If it was just your aura, like Ben said, it would mean that anyone low on aura couldn't use their Semblance. If the reason Weiss got her scar was because she was punched in the White trailer (she had low aura), this couldn't be true, as we see her use air-step later on in that fight.