Abstract

Legislative text translation requires unusually high fidelity because terminological substitutions, modal shifts, and discourse-level reformulations may alter rights, duties, or institutional meaning. While Large Language Models (LLMs) and multi-agent systems have advanced general-purpose translation, their probabilistic generation processes remain weakly aligned with the constrained interpretive conditions of statutory language. Existing agentic frameworks, which primarily rely on horizontal collaboration among peer agents, often improve fluency without providing sufficient vertical control over the layered structure of legal language. This paper proposes HL-Trans, a Hierarchical Control Framework for legislative translation that operationalizes fidelity through three progressively constrained layers: terminology anchoring, syntactic shaping, and discourse polishing. Rather than treating Skopos theory as a license for free functional adaptation, we reinterpret the legislative translation brief as a constrained functional objective: the target text should preserve legal concepts, deontic force, and institutional genre while remaining subject to expert human review. Experiments on a Chinese-English-Japanese legislative corpus show that HL-Trans improves terminology consistency, deontic modality preservation, and discourse conformity over strong LLM and multi-agent baselines. The analysis further identifies a “Gain-Interference-Rescue” pattern: terminology constraints first improve conceptual fidelity; syntactic constraints may temporarily reduce surface fluency while protecting legal force; and discourse-level polishing can restore readability without relaxing lower-level constraints. The results suggest that hierarchical control is a promising design principle for trustworthy legal translation, while also underscoring the continuing need for transparent resources, expert validation, and accountable human oversight.