The bill requires a pharmacist to list each ingredient in the compound and certify the product with a signature.
But Carmelo Cinqueonce, executive vice president of the S.C. Pharmacy Association, said it was unclear what problem the bill, S. 453, sought to solve.
In Aiken County there are nine polo clubs recognized by the United States Polo Association and about 40 fields, according to the Aiken Polo Club's Web site.
Sanford objected to a part of the bill that had nothing to do with polo horses.
The governor pointed to the provision that would grant only residents who live within two miles of a livestock operation the right to appeal a state livestock permit. An appeal that was decided in court could then affect every state resident, undermining local control, Sanford warned.
Lawmakers will return June 16 to consider overriding the governor's vetoes.