Sen. Wayne Allard, R-Colo., a veterinarian, is introducing legislation at the request of the Humane Society that would close a loophole in the Animal Welfare Act that allows birds to be shipped across state lines if cockfighting is legal in the state receiving the animals. New Mexico, Louisiana and Oklahoma are the only states where cockfighting is still legal. Missouri and Arizona voters banned the practice this past November. The Humane Society said cockfighting still takes place, however, in many states where it is banned.

Cockfighting opponents say breeders will often claim they possess birds not to fight in their own state but to take them to a state where cockfighting is legal. The claims often cause confusion for law enforcement officials and result in no prosecution, activists say. "The fact that there's not an interstate trade prohibition on the birds and the paraphernalia is a big opening for cockfighters to exploit," Pacelle said. Added Humane Society investigator Eric Sakach, "Our experience has shown virtually no state is immune."

In the centuries-old activity, fighting roosters outfitted with blades on their heels are placed in a ring to slash at each other while spectators often bet on the outcome. The loser of the fight often dies. "These animals have no choice," said World Championship Wrestling champion Bill Goldberg, an Oklahoma native who is featured in advertisements denouncing the practice. "It's sick."