I get it, to a certain extent... When you are training or weight training these days in a serious manner, you have to use the crazy supplements and shakes and soforth to keep up with the joneses... problem is, many of these supplements contain ingredients that, while legal to sell in any GNC or other fitness or supplement provider, is not necessarily a legal substance by the laws of whatever governing body oversees your drug testing. If your trainer tells you to take something, you take it in other words. It is on him and he knows what the best course of action is and quite frankly many athletes probably aren't literate enough to read the 2 page ingredient list of xyz supplement, let alone the 60 supplements they are pouring into their bodies.
That said, it shouldn't be that hard to pay a trainer or doctor to review the policy and your supplement regimen to ensure compliance.