When I started competing in the INBF/WNBF, there was a whole list of supplements that even though perfectly legal, are "banned". HOT-ROX was right there on it. Various other natural bodybuilding federations, and I would assume non-professional level sports leagues have their own stances on products that can be viewed as possibly controversial.
Also, and this is something interesting to think about, I've been working with a lot of physique athletes for a while now, but the last year, I've been approached by more actual performance athletes for nutrition and training advice. Now, that a fairly well respected performance Center that caters to a lot of professional as well as high school and collegiate athletes refers people to me, they made it very clear that I should avoid recommending ANY specific supplements to athletes of any level. With so much money on the line for the pros, and scholarships on the line for the student athletes, the last thing anyone wants is for an athlete who decides on their own to use PEDs, gets caught, and blames it on something his "trainer recommended".