Something that should clue you in is where you buy the stuff. If you have to go down dark alleys or get it from a "friend" at the gym odds are it is illegal. If you go to the store and buy it you can be pretty sure it is legal. The issue actually becomes that your body will urinate the excess out causing you to show up positive certain physical issues. I had that issue when I left the military. Fortunately I had the physical far enough in advance that I was able to take a week off from the gym and supplements and re-pee.
If you base your decision on what is legal for the Olympics you will find most things are regulated by the IOCC, but not necessarily illegal. You can't even have caffeine in your system and compete in the Olympics. The no caffeine rue is why I never became a Olympic athlete (that and the complete lack of talent:D).
But when a long train of abuses and usurpations, pursuing invariably the same object, evinces a design to reduce them under absolute Despotism, it is their right, it is their duty, to throw off such Government, and to provide new guards for their future security.
Translation for the intellectually challenged: If the government screws the people too much, it is the right and duty of the people to revolt and form a new government.