But I guess it comes down to where you draw the line as what's a "performance enhancing" drug. I know a lot of people who use like protein drinks and whatnot after training because they're trying to build muscle. Which could most certainly be considered "performance enhancing" but is entirely legal.
That, and it's not a drug. The testing policies clearly define what is going to be considered a banned performance enhancer - most center around forms of anabolic steroids, HGH, and amphetamines - because those are drugs.