27 C.F.R. § 10.21
It is unlawful for an industry member, directly or indirectly or through an affiliate, to induce a trade buyer to purchase the industry member's products, to the complete or partial exclusion of products sold or offered for sale by other persons in interstate or foreign commerce, by offering or giving a bonus, premium, compensation, or other thing of value to any officer, employee, or representative of the trade buyer. The bonus, premium, compensation, or other thing of value need not be offered or given for the purpose of directly inducing a trade buyer to purchase from the seller, but rather is applicable if an industry member induces officers, employees or representatives of the trade buyer to promote sales of the industry member's products and thereby indirectly induces the trade buyer to purchase from the industry member.
27 C.F.R. § 10.21