(a) A nonresident brewer's agent may not represent a nonresident brewer unless the agent is the primary American source of supply for a product produced by the nonresident brewer.
(b) In this section, "primary American source of supply" means the nonresident brewer or the exclusive agent of the nonresident brewer. To be the "primary American source of supply" the nonresident brewer's agent must be the first source, that is, the brewer or the source closest to the brewer, in the channel of commerce from whom the product can be secured by Texas distributors.