The L-Metric Boundary and the Realized Physical Interior This paper develops an AASC account of when metric structure may legitimately function as physical description. It asks a prior question to ordinary metric physics: Under what structural conditions may distance, duration, locality, propagation, curvature, scale, and metric-dependent parameters carry physical standing at all? The paper does not reject metric geometry, Lorentzian structure, fields, particles, quantum records, or cosmological parameters. It distinguishes their lawful use inside a realized physical interior from any claim that metric structure can supply its own primitive authority before that interior has been licensed. The L-metric boundary The paper defines an L-metric boundary as a locally minimal projection interface at which metric descriptors first become physically interpretable within a fixed dependency order. “First” is not temporal. It means minimal in the relevant projection order. The L-metric boundary is not itself a spacetime surface, causal event, measurement interaction, or dynamical mechanism. It is an interface role at which already standing-positive physical content can be articulated using metric predicates. The paper distinguishes two readings: a generative reading, in which the boundary creates or ontically grounds metric structure; a licensing reading, in which the boundary authorizes the lawful use of already qualified metric content. The theorem establishes the second reading. The L-metric boundary licenses metric description without generating metric structure, standing, or physical ontology. The L-metric licensing theorem The paper constructs a canonical licensing relation from complete original metric-use records. Each record retains: its original act and physical relata; the metric descriptor being used; its target interpretation; its complete result graph; its original application domain; its joint conditions; its calibration and unit transport; its continuation obligations; its boundary-work and historical attribution. A greatest safe region is then constructed by a monotone continuation operator: Sᴰ = Φᴰ(Sᴰ). This region contains precisely those metric-use records whose local conditions, declared redescriptions, lawful transports, and finite retained continuations are all warranted. The licensing relation is the projection of that safe region: Licᴰ = {(α(c), μ(c)) : c ∈ Sᴰ}. The central theorem proves that every admissible same-scope use of a metric descriptor belongs to this relation and satisfies five independent conditions: domain qualification; lawful redescription and metric transport; preservation of original boundary work; continuation compatibility; non-generativity. Conversely, a record in the safe region supplies a sound admissible articulation for its original metric-use task. In plain terms: admissible interpreted metric use ⇒ licensed metric articulation. The original physical incidence supplies the qualification. The licensing relation records its lawful metric description. No metric backflow The paper proves a no-backflow theorem. An interior metric fact cannot generate or alter qualification at an unchanged original incidence, nor can it supply its own missing target-specific license through circular dependence. This excludes several distinct errors: treating successful use as the source of the qualification required for that use; treating covariance or geometric elegance as primitive authority; using a metric result to repair a failed original occurrence; extracting a new source-level distinction from data that do not retain it; allowing a horizon, singular surface, cutoff, or causal boundary to authorize itself merely by geometric designation. The theorem does not prohibit later evidence, repaired apparatus, new experiments, sound constructor theorems, or newly qualified physical uses. It distinguishes later discovery of an unchanged qualification from alteration or replacement of the original conditions. Metricity, locality, and the pre-metric interior The paper shows how licensed locality can precede numerical metric articulation. A pre-metric locality role may involve standing-localization, bounded dependence, restoration, continuation neighborhoods, or admissible transport paths. Metric locality requires additional admitted relata, comparison structure, and target-specific preservation conditions. A pre-metric joint-standing relation is therefore not refuted merely because a later metric-locality condition has not yet been established. The paper also distinguishes structural bounded transport from a quantitative finite-speed law. A continuation-neighborhood result does not automatically supply a finite propagation velocity, causal cone, or dynamical law. Those stronger conclusions require their own temporal, metric, and physical hypotheses. Physics-bound audits The foundational licensing theorem is tested against several physics-facing applications. These audits are independent applications of the licensing rule, not premises of its proof. The paper examines: Lorentzian interval comparison and the requirement for standing-positive relata; zero-point vacuum energy and quotient-stable scalar prediction; structural versus numerical claims in the Standard Model; cosmological parameter comparison and Hubble transport closure; entanglement, joint standing, and the absence of an automatically supplied controllable channel. These applications preserve the distinction between structural licensing and physical realization. A failure or revision in one audit affects that application’s source hypotheses; it does not by itself alter the central L-metric licensing theorem. Relation to standard physics The paper is not a replacement for: Lorentzian geometry; general relativity; Bell-type locality analysis; quantum no-signaling theorems; renormalized stress-tensor theory; Standard Model parameter determination; cosmological model comparison. It supplies a constraint-theoretic account of when such structures may function as standing-bearing physical description within a realized interior. Metric objects, fields, particles, records, gauge structures, and curvature may be physically real as role-stable interior content. What is denied is primitive boundary status: the ability of a metric or metric-dependent object to authorize the regime in which it is used merely by being asserted or successfully applied. Scope and non-claims The results are exact relative to the stated original-use profiles, application domains, joint conditions, continuation contract, and AMetric exclusion discipline. The paper does not claim: to derive general relativity or quantum dynamics; to derive the full Standard Model parameter table; to solve the cosmological-constant problem; to adjudicate unrestricted ΛCDM model selection; to derive quantum no-signaling from quantum dynamics; to prove global uniqueness of every possible L-metric interface; to guarantee that every proposed metric-use contract has a nonempty realization; to establish a universal metric, unique physical occupant, or complete future theory. A missing interpretation, omitted required use, invalid transport inference, incomplete continuation contract, or absent physical realization remains open to direct criticism. Role in the AASC programme This paper provides the metric-licensing layer of the AASC corpus. It carries the AASC kernel and AMetric boundary discipline into the realized physical interior, defining the interface at which metric physics becomes lawful without becoming primitive. Its principal contribution is to formalize the distinction between: metric structure and metric authority; physical realization and descriptive licensing; dependence of an answer and dependence of its warrant; pre-metric locality and metric locality; later discovery and retroactive repair; interior physical content and boundary authorization. The resulting endpoint is a disciplined account of metric physics as licensed description: The metric boundary licenses lawful interior articulation; it does not generate the metric structure, standing, or ontology that the description presupposes. Keywords L-metric boundary; metricity as licensed description; AASC; AMetric boundary; admissibility and standing; realized physical interior; metric licensing; no metric backflow; fixed-domain identity; lawful redescription; continuation compatibility; pre-metric locality; Lorentzian comparison; quantum no-signaling; cosmological transport