Like a lot of star athletes, cyclist Lance Armstrong racked up many a product endorsement deal along with his big wins. But on Wednesday—a week after the U.S. Anti-Doping Agency published a report on allegations that Armstrong was part of a doping ring—his brand-backers started backing away from the seven-time Tour de France champ. Nike, Trek Bicycle, Easton-Bell Sports, and a score of others all bid Armstrong and his tarnished image goodbye.

Endorsement agreements between companies and athletes can be high-risk, high-reward propositions. Corporations are banking on a positive association with the star. Though—as the Armstrong case shows—there’s still plenty of room for things to go wrong. And when they do, says Richard Grant, managing partner of the McGuire Woods Los Angeles office, “it’s critical that the brand be able to take action to protect themselves.”