Paper 9, The Emergence of Classical Law, is the third and final part of the trilogy Publication Series: The Physical Consequences of Postulate P1. This trilogy extends the six‑paper ontological sequence by developing the physical implications of Postulate P1: the principle that a system which is unmeasurably large and closed is necessarily also unmeasurably large and open. Within this framework, physical reality emerges as a representational layer that remains structurally incomplete, with the remainder term χ expressing the persistent openness of any domain. This final paper shows how classical physics arises as the maximal‑coherence limit of P1. When representational domains approach closure, coherence becomes rigid enough to produce the structures recognised as spacetime geometry, causal order, conservation laws, and the symmetries of the Standard Model. These are not fundamental layers of reality but stability regimes that emerge when the remainder term χ becomes small while never vanishing. General relativity and the Standard Model appear as high‑coherence limit‑projections of the same representational architecture that, in lower‑coherence regimes, yields quantum multiplicity and reconfiguration. The cosmological constant Λ is identified as the persistent signature of structural incompleteness, linking microscopic openness to large‑scale geometry. With this, the physical interpretation of P1 reaches closure: classical law is an emergent projection of a universe that remains fundamentally open. This trilogy builds on the six‑paper ontological foundation The Articulation of Postulate P1. The present work completes the physical development of P1 by showing that classical physics is not fundamental but a high‑coherence stability regime of an open representational architecture.