If a principal makes a revocable offer of a commission to a sales representative who is not an employee of the principal, the sales representative is entitled to the commission agreed on if: the principal revokes the offer of commission and the sales representative establishes that the revocation was for the purpose of avoiding payment of the commission; or the revocation occurs after the sales representative has obtained a written order for the principal’s product because of the efforts of the sales representative; and the principal’s product that is the subject of the order is shipped to and paid for by a customer. This section may not be construed to: impair the application of § 2-201 or § 2-209 of the Commercial Law Article; abrogate any rule of agency law; or unconstitutionally impair the obligations of contracts.