491.101A Poison pill defense authorized. The terms and conditions of stock rights or options issued by the corporation may include, without limitation, restrictions or conditions that preclude or limit the exercise, transfer, or receipt of such rights or options by a person, or group of persons, owning or offering to acquire a specified number or percentage of the outstanding common shares or other securities of the corporation, or a transferee of the offeror, or that invalidate or void such stock rights or options held by an offeror or a transferee of the offeror. 89 Acts, ch 288, §187
Iowa Legal Code