We have all heard stories, or perhaps even witnessed, scandals involving prominent yoga teachers, gurus, and lamas. Many such scandals have left behind fractured communities and broken lives. Some defend such leaders, drawing a sharp distinction between their teachings and their conduct. Others reject the notion that character can be separated from spiritual depth, arguing that their conduct reveals the unreliability and inauthenticity of their teaching. What then is, or should be, the relationship between ethical conduct and the authentication of teachers' authority in yogic traditions? Does unethical behaviour by a yoga teacher, guru, or lama diminish or even invalidate their teachings? In the Abrahamic traditions, there is a close coupling between purported spiritual advancement and an expectation of moral conduct. When abuses happen, they are usually evidence of a clear breach of the teachings of the tradition. In some yogic traditions, that also holds true. In others, things are not so clear. A variety of factors complicate the ethical teachings of some yogic traditions, including different views of karma, different perspectives on the reality or unreality of the phenomenal world and other people, beliefs in ‘crazy wisdom', guru yoga, the pursuit of yogic powers or siddhis, and so-called ‘left-hand' tantric traditions. To illustrate aspects of these themes and the diversity of perspectives among yogic traditions, this presentation will draw on five traditions: Patañjali's Yoga, Nondual Śaivism, Advaita Vedānta, Theistic Vedānta, and Tibetan Buddhism. I argue that giving due attention to the implicit metaethical philosophies of different traditions is crucial for yoga scholars, teachers, and students seeking to understand how communities negotiate authority and authenticity in both traditional and modern yogic settings.