Indiana Code Title 24. Trade Regulation § 24-1-3-1

Sec. 1. A person who enters into any contract or combination to induce, procure, or prevent any wholesale or retail dealer in or manufacturer of merchandise or of supplies or of material or articles intended for trade or used by any mechanic, artisan, or dealer in the prosecution of his business from selling such supplies to any dealer or to any mechanic or artisan commits a Class A misdemeanor.  A dealer in or manufacturer of such supplies, material, or articles who is a party to any such contract or combination or who upon the request of any party to any such contract or combination refuses to sell such supplies, materials, or articles to any other person who may require them in the prosecution of his business, for the reason that the other person is not a member of a combination or association of persons, commits a Class A misdemeanor.  All such contracts and combinations are void.