In this paper, we propose the high frontier as a distinct and understudied domain of spectrum governance and develop an institutional framework for analyzing it based on the theory of property rights mismatch. We conceptualize the high frontier in terms of the following features: global mobility, persistent overlap of active and passive users, and interference-sensitive coexistence. This domain encompasses the Ka-band, mmWave frequencies, and low Earth orbit satellite regimes, where the convergence of large numbers of satellites plus advanced transmission technologies and passive scientific services exposes deep tensions in existing spectrum property rights frameworks. Drawing on the theory of property rights mismatch, we show how the current institutional features of spectrum governance – parcelized rights, national licensing regimes, and transmitter-centric rules – do not align with the resource characteristics of the high frontier: non-excludability, cumulative interference, and mobility-driven spillovers. Unlike earlier applications of property rights mismatch that focused on terrestrial mismatches or contractual solutions such as virtual parceling, this paper situates the high frontier as a global commons that requires new governance architectures. We organize our analysis around the technical and institutional dimensions of mismatch and propose governance innovations that align spectrum rights with the unique conditions of the high frontier.