My bud says he got a kangy with drain punch from some guy on facebook in late decmber so I was wondering with all the pokebank chaos, if it's legal?
Yes, it is. Kangaskhan can by taught Drain Punch by the move tutor in Humilau City in B/W 2 for 10 Yellow Shards. So you can get it in X and Y if you use PokeTransporter.
The FB dude could have transported that Drain Punch Kangaskhan from Unova to Kalos by PokeBank. It is legal.