The Architecture of Definition: Semantic Instability, Domain Clashes, and Institutional Manipulation in Regulatory Governance

Administrative definitions determine the scope of regulatory duties, protections, and coercive powers, yet public-law analysis often treats definitional instability as a matter of interpretation rather than as a recurring governance risk. This article proposes a structured diagnostic framework for analysing when changes in regulatory language, cross-domain reclassification, and uneven implementation may undermine legal certainty and administrative accountability. The framework distinguishes three stages: an initial audit of circularity, boundary uncertainty, and unsupported category substitution; an assessment of semantic instability and application asymmetry across time or institutions; and a provisional evaluation of institutional advantage in light of alternative, non-strategic explanations. It introduces an exploratory Epistemic Degradation Index (EDI) as a coding heuristic for organising evidence, while expressly rejecting any claim that the index proves unlawfulness, bad faith, or manipulation. Four illustrative scenarios, drawn from unrelated regulatory sectors — telecommunications, labour and tax classification, banking supervision, and customs — demonstrate how the framework can distinguish ordinary regulatory maintenance from patterns warranting closer public-law scrutiny. The article concludes that the framework is best understood as an evidential and analytical aid that may support existing inquiries into legality, rationality, procedural fairness, and improper purpose, rather than as a new independent ground of judicial review. This is the third draft version Version 3 Change Log - Rewrote the abstract to emphasise evidential use, legal uncertainty, and multi-sector applicability. - Added explicit separation between terminology standards, logic concepts, and UK public-law doctrines. - Expanded the Substitution Rule section with four clarifications on purpose, evaluator judgment, consequence-based analysis, and limits of biconditional reasoning. - Reworked the Primary Level taxonomy to include Economic/Functional and Historical domains, with explicit caveats on overlap and non-exhaustiveness. - Added detailed cautions explaining when domain-crossing is legitimate and when it becomes a Category Error. - Introduced a revised definition of Category Error focusing on failure to supply independent, positive criteria rather than domain movement. - Added Table 1 clarifying what each diagnostic finding does and does not establish in law. - Recalibrated EDI scoring definitions, especially the E column, to emphasise unsupported domain substitution rather than domain crossing. - Added four new hypothetical scenarios (telecommunications, labour/tax classification, banking supervision, customs) to demonstrate cross-sector applicability. - Strengthened disclaimers that the framework is an evidential aid, not a standalone ground of judicial review.