I need some help from USA legal folks...

Recently I found possibility to trade several dozens USA based accounts through OANDA.

I need to know if it is legal for me , non USA citizen without NFA registration, to trade these accounts only based on Limited Power of Attorney?

a) is it legal to advertise for USA citizens
b) is it legal to trade such accounts
c) what is possible scenario for me to do this?

I need this info very bad... don't want to mess up with law.

Andrew