One of the most controversial issues in administrative law, the use of guidance, is exemplified by the regulation of one of the most controversial areas in modern society: genetically modified (GM) food. The appropriate use of guidance versus notice and comment rulemaking is a much-debated issue in administrative law. While agency officials generally assert that they are using guidance to express an agency’s thoughts about how to comply with a specific statutory provision or agency rule, the practical consequence is that the regulated party will hesitate to disobey, even if it believes that the guidance goes beyond the requirements of the statute or rule. The Food and Drug Administration’s (FDA) regulation of GM food through a guidance document provides a prime example of this effect: the document recommends a premarket review process that the FDA describes as voluntary for firms attempting to bring a new product to market. The reality is that regulated parties feel compelled to comply. This is a controversial and questionable result because many types of genetic modifications are well understood and pose no safety issues; the scientific consensus is that GM foods currently available are as safe as non-GM foods. This situation raises the central issue addressed by this Article: how to determine whether an agency is appropriately using guidance, or whether the agency should be required to use notice and comment rulemaking. After discussing why the current theoretical approaches3⁄4interpretation and bindingness3⁄4are inadequate to solve this problem, this Article proposes a new theoretical framework in which to answer this question of public controversy to determine when informal rulemaking with notice and comment is advantageous and even required by the Administrative Procedures Act (APA). This new theoretical framework is then applied to the controversial issue of GM food.