this could go so many ways...I think if you are trying to improve your body/mind by using AAS responsibly, then aren't you being a good steward of a body (that's not yours anyway)?
Testosterone improves bone density, lowers body fat, lowers cortisol and insulin levels, combats depression, promotes good skin and helps brain functions. These are all good things.
So, I guess its up to your personal convictions. For some Christians, drinking even a drop of alcohol convicts them. I personally think they are living in bondage. Jesus' first miracle was turning water into wine (at a wedding). What are you feeling about this issue? Do you feel heavily convicted not to use AAS?
As for the legality issue...genarr3 had a good point. Do you cheat on your taxes? Do you break the speed limit? Run red lights? Fail to stop at a stop sign? How about fornication? Ever had sex outside of marriage? I'm not saying any of these are right. But, come on...are you really struggling with this? And, how does this compare with other areas of your life?
I certainly dont believe you'd be breaking any commandments. Remember what Jesus said, "Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind. This is the first and great commandment. And the second is like unto it, Thou shalt love thy neighbour as thyself. On these two commandments hang all the law and the prophets." (Matt 22:37-40)
So, love God...and love others. Pray about it. If you feel like God is "telling" you not to use AAS, then don't. If you feel you can benefit from them and by benefitting, better serve God...