Nowhere in the complex labyrinth of rules, bylaws and interpretations that govern the global anti-doping system did anyone see this warning: Beware of Dog Medicine.

It's an understandable omission, but one that led to a three-month sleuthing expedition that eventually exonerated a five-time Olympian of doping, while adding what some feel is an unnecessary asterisk next to her spotless record as a clean athlete.

Katerina Nash, a mountain biker and cross-country skier who represented the Czech Republic in two Winter and three Summer Olympics, avoided a four-year doping sanction after minute trac...