In theory yes it could be illegal, but for personal use I would bet my paycheck the DEA are not going to be knocking on your door,unless it's one of those "Media Hype Drugs" that everyone is talking about if you know what I mean.
Just do your thing and don't worry, his friend is either imaginary, or was getting alot for resale.
This is only my opinion, you should get more.
Goodluck.