Background: Over the past decade, courts and administrative agencies increasingly have considered cases that involve clashes between charter school proponents and teacher unions. While these cases have focused on a range of education policy issues, some cases have focused on arguably the most important legal and policy distinction applicable to charter schools--whether a charter school should be considered public or private. Purpose: This study examines the intersection of the public/private distinction in U.S. law and policy, and the shifting political positions of teacher unions and charter school proponents, in courts and agencies. We examine the history of the public/private distinction in U.S. law and policy and specifically in education, in addition to conducting an in-depth analysis of three recent decisions involving charter schools and teacher unions in which courts and agencies determined whether charter schools were public or private organizations. Research Design: This article is a legal analysis and historical case study. Findings: Three recent and high-profile education cases in agencies and courts reflect the continuing breakdown of the public/private distinction in law and policy. Courts and agencies have hinged their decisions about the applicability of federal and state collective bargaining laws on this distinction and have grounded decisions about the basic constitutionality of state charter school laws in this distinction as well. However, there is little consistency in how the public/private distinction has been applied in legal clashes between teacher unions and charter schools. Conclusion: Our analysis underscores the limitations of the current debate over the public/private nature of charter schools and teacher unions, particularly in the institutional settings of courts and agencies, because this debate is largely untethered from issues of teaching and learning. However, our analysis also suggests that the public or private nature of charter schools still appears "up for grabs" in the legal arena. As such, courts and agencies might offer reformers a useful venue compared to the legislative arena for influencing how the public/private distinction applies to charter schools.