A number of lumber retailers formed an association to promote their interests. Some of the lumber retailers turned in the names of lumber wholesalers who sold directly to the public. This practice had a negative impact on the retailers by increasing the competition. The association would distribute to the members the names of those wholesalers in hopes that the retailers would not do business with the wholesalers who sold directly to the public. After receiving the information, many of the retailers refused to do business with the wholesalers who sold directly to the public. The association had no enforcement mechanisms and there was no evidence that the boycott of the lumber wholesalers who sold to the public caused any loss of business. Is this a violation of §1 of the Sherman Act and, if so, is it subject to the per se rule or the rule of reason? Explain.