Why can't you eat horse meat in the U.S.?

The first sentence of Repugnance as a Constraint on Markets asks "Why can't you eat horse meat" in California? The answer is that it's against the law. But while similar bills to outlaw the sale of horse meat for human consumption have passed by big majorities in the U.S. House of Representatives, they have never managed to pass into law. Nationally such bills are opposed (as they were in California) by many horse breeders, cattle ranchers, and veterinarians. Nevertheless, the department of Agriculture removed funds for inspection of slaughterhouses.

Now the NY Times reports: Surge in Abandoned Horses Renews Debate Over Slaughterhouses .

"Emaciated horses eating bark off trees. Abandoned horses tied to telephone poles. Horses subsisting on feces, walking among carcasses.
As the economy continues to falter, law enforcement officers in Kentucky and throughout the country are seeing major increases in the number of unwanted and neglected horses, some abandoned on public land, others left to starve by their owners.
The situation has renewed the debate over whether reopening slaughterhouses in the United States — the last ones closed in 2007 — would help address the problem. Some states, Missouri, Montana and North and South Dakota, for example, are looking at ways to bring slaughterhouses back. "