As RSEs, we aim to develop research software in a way that makes it reusable by others. Sometimes, the community of users and contributors around our reusable software grows quickly, while the number of people maintaining the software stays the same, and is often very small to begin with. In this situation, our decisions about the software and the project may affect many more people than anticipated. This calls for a formalization and communication of how we make and enforce decisions within the project, i.e., governance. When we devise governance, there may be many open questions, some of them rather philosophical: What is the actual mission of the project, what are its aims and scope? What are the foundational principles of our project, especially for interacting with different roles in our community? What requirements do we need our model of governance to support? Practical questions follow: What organizational structures do we need? How should these structures interact with each other? What are the processes we need, and how do we implement them? Who gets to decide what? What are the risks, and what do we do if something goes wrong? How can we ensure that governance does not add too much to the already heavy workloads of the people that are involved? And finally: How do we document and enforce all of this? In this talk, we share experiences from recent work to design and implement governance for the Citation File Format project, and some challenges we faced.