Dark energy is inferred observationally as a persistent, approximately homogeneous contribution to the late-time expansion of the Universe, yet it remains undetected in ordinary matter-sector channels. Standard approaches encode this component as an effective energy density, vacuum term, or dynamical field, often implicitly assuming a material ontology. This paper re-examines dark energy at the level of lawhood rather than microphysical modeling, using the Tier-0 admissibility framework as a structural diagnostic. Within this framework, admissible physical structure is defined by closure, persistence, and boundary normalization, independent of interpretive or model-dependent assumptions. We show that the defining empirical profile of dark energy global curvature influence, non-clustering behavior, and systematic silence with respect to dissipative record formation, is structurally incompatible with a conventional record-bearing substance. Instead, dark energy is classified as a closure-stable background contribution: gravitationally active, non-localized, and silent with respect to ordinary detection channels. This classification preserves standard gravitational dynamics and the effective utility of ΛCDM parameterizations while clarifying why direct non-gravitational detection is not generically expected. The result is not a new dynamical model, but a law-level reorganization that constrains admissible interpretations of cosmic acceleration without modifying established physics. This work is a companion to Dark Matter as Record-Silent Curvature: A Law-Level Classification Within the Tier-0 Framework (Zenodo DOI: https://doi.org/10.5281/zenodo.18261716), which applies the same admissibility criteria to the structural classification of dark matter. Together, the two papers clarify how distinct observational profiles can arise from different admissible curvature roles without modifying established gravitational dynamics.