you can apply it, but it becomes soulbound now. You could try the "unbind" exploit, but you do so at your own risk (and I believe that the item needs to have a durability rating).
If the PTR 3.1 changes go though, then you may as well not bother. Blizz is moving away from the "Grandfathering" method and embracing level requirements for item enhancements, including librams, enchants, patches and the like.
