That's an interesting question, since while making your body stronger using chemicals seems like cheating in physical sports, is making your brain smarter the same sort of thing? Your intelligence seems much more intrinsic to how we define what 'you' are, while your body seems a bit more separate, so priming it with substances seems more like cheating. If I make myself a better chess player by reading chess books, that's not cheating, but by making myself chemically more able to understand and apply what I read in chess books, that is?
Also, whatever the ethics of it, using cognition enhancing substances is not yet illegal in chess, so people could use those until their use is somehow banned. In addition, tests for blood levels of the full variety of nootropics would be difficult to develop.
Nootropics are drugs or supplements which have some demonstrated capacity to improve intellectual skills, and there are people who take them regularly to advance in their careers, as well as forums dedicated to sharing information about them. Since chess is an intellectual game, I wonder if anyone has ever tried nootropics to improve chess skills or aptitude? To take one example, krill oil has been found in one study to improve spatial reasoning in rats, so since spatial reasoning is involved in chess, perhaps it would be beneficial to players.