People deliberately injure show horses to improve their performance in the ring. Soring is the practice of fastening heavy chains or similar equipment, called action devices, on a horse's front limbs. From this, the horse may suffer intense pain as its forefeet touch the ground. This pain causes it to adopt a high-stepping gait that is highly prized in Tennessee walking horses and certain other breeds. In the Horse Protection Act, Congress sought to end this practice by forbidding the showing or selling of sored horses. Exercising broadly phrased rulemaking power D issued regulations that prohibited soring devices and other soring methods in both general and specific terms. Violations may result in both criminal and civil penalties. Use of painkillers may make detection of actual soring difficult. P contends that developments since these regulations have demonstrated their inadequacy and petitioned D to revise them in a new rulemaking. P cited an extensive study conducted at the Auburn University School of Veterinary Medicine between September 1978 and December 1982. Many of the devices not outlawed by current regulations fell within the statutory definition of sore. The use of such 'legal' devices can reasonably be expected to cause pain and suffering to the horse, including distress, inflammation, or lameness when walking, trotting, or otherwise moving. D denied P’s petition. The district court granted summary judgment, and P appealed.