Professor Bayern's research focuses on the common law, primarily in contract law, tort law, and organizational law. He teaches Torts, Contracts, Agency & Partnership, and other related courses.

His research has criticized formalism and other economic simplifications of the law. For example, in The Analytical Failures of Law and Economics (Cambridge University Press, 2023), he surveyed leading law-and-economics arguments and showed them to be fragile, self-contradictory, or otherwise problematic. His research has also offered creative transactional solutions to legal problems. In Autonomous Organizations (Cambridge University Press, 2021), he showed that modern LLCs are flexible enough to give legal personhood to software and considered the consequences of that capability. 

Professor Bayern is also the author of an introduction to the common law titled Principles and Possibilities in Common Law (West Academic, 2023) and, with Mel Eisenberg of Berkeley Law, of the Gilbert Law Summary on Contracts (West Academic, 15th ed. 2021). He is an elected member of the American Law Institute and serves as adviser to the Restatement (Third) of Torts: Miscellaneous Provisions and the Restatement (Third) of Torts: Medical Malpractice.

Before joining FSU Law, Professor Bayern was a visiting assistant professor at Duke Law School. He has also visited at Berkeley and Northwestern’s law schools. As a law student, he was editor-in-chief of the California Law Review and a recipient of the Thelen Marrin Prize for Academic Achievement, given annually at graduation to the student with the strongest academic record. Before his legal career, Professor Bayern worked in computing research, served on groups responsible for developing programming languages, and wrote several books and articles about computer programming. He also created the Central Authentication Service (CAS), a software framework for computer security that has been adopted by many universities, including Florida State.  He served as associate dean for academic affairs at Florida State from 2019 to 2023.