Critical Arrow Glitch?

So, a few of my family members play PWI as well, and my Dad just found out if you equip a bow, and a 1%CH arrow, then take the bow off, the 1% stays. He's telling me that this isn't illegal, because his ex-Guild Leader has been doing this since he began playing.

Some clarification, please?
He doesn't believe me when I tell him that it sounds pretty illegal.