The first thing to understand about bodybuilding supplements is that they are a SUPPLEMENT. In other words, don't take them as the first measure of your bodybuilding routine.
If you expect the supplement to do what your workout routine is supposed to do, then you are going to be disappointed or, worse, you could find yourself in deep trouble medically.
Like many other things, bodybuilding supplements can be harmful if misused. If you take them in excessive amounts or too often, then they could be harmful.
If you take them and don't actually do any physical workout, for which they are intended to be a supplement, then you are misusing them.
No they're not. Why would national chain stores sell them if they were not legal?
They'd be put out of business or slapped with hefty fines for doing so, maybe both. In actuality, certain sports organizations have banned them for use by their athletes, but you can still buy them over the counter because they are perfectly legal.
Still, you must educate yourself on their proper use. The best otc supplements are those that have stood the test of time. The same can be said for workout routines. Keep yourself safe and sane.
The problem many novice bodybuilders have is that they think they can circumvent the workout process and use bodybuilding supplements to build up body mass and stay fit without doing any physical exercise.
The truth is, if you don't do any working out at all and you use bodybuilding supplements, then they won't have any effect. You might as well just be taking a placebo. They only work if you are physically active and managing a consistent workout routine.