This paper presents a law-level structural explanation of superconductivity, reframing dissipationless transport and magnetic flux exclusion as consequences of universal admissibility conditions rather than as effects tied to specific microscopic mechanisms. Building on the Tier-0 / Everything Equation framework, the work identifies superconducting phases as structurally closed sectors in which irreversible collapse acts trivially. Boundary normalization, collapse persistence, and closure under admissible transformations together enforce macroscopic coherence once the relevant spectral conditions are satisfied. Rather than proposing a new material model or modifying established microscopic theories, the paper explains why superconducting phases, once realized, are protected from dissipation by law-level structure. Conventional theories such as BCS and Ginzburg–Landau are shown to operate within this admissible sector, providing realization mechanisms without determining the persistence of coherence itself. The analysis demonstrates that dissipationless transport is not prohibited by physical law at ambient conditions, but is constrained by structural admissibility. Superconductivity is thus identified as a lawful fixed point in physical theory space, selected by closure rather than by material anomaly. This work complements existing experimental and theoretical research by providing a universal structural account of superconductivity that applies across materials, temperatures, and pressure regimes, without introducing new physics or altering established dynamics.