Copy Less, Ground More: Selective and Confidence-Aware Decoding for Grounded Legal Generation

Tan-Minh Nguyen, Truong Dinh Do, Hiep K. V. Nguyen, Le-Minh Nguyen


Abstract
While retrieval-augmented generation (RAG) grounds large language models (LLMs) in external knowledge, ensuring faithful evidence utilization in complex domains like law remains challenging. LLMs often ignore retrieved facts or indiscriminately copy from noisy contexts. Existing context-aware decoding methods attempt to mitigate this by amplifying the influence of retrieved content, but they treat the context as a monolithic block—amplifying irrelevant spans alongside evidence—and intervene at every decoding step, incurring substantial inference overhead. To address this, we propose SaCoD (Selective and Confidence-aware Decoding), a training-free inference framework. SaCoD leverages the LLM’s internal attention signals to dynamically isolate salient evidence paragraphs at each step, restricting a customized copy mechanism strictly to relevant facts. Furthermore, an entropy-based gate activates this intervention only when the model is uncertain, bypassing copy operations for deterministic tokens to preserve linguistic fluency and cut computational overhead. Experiments on four legal question-answering benchmarks across three open-weight LLMs demonstrate that SaCoD significantly improves faithfulness and response correctness while substantially reducing inference latency compared with prior context-aware methods.
Anthology ID:
2026.findings-aacl.158
Volume:
Findings of the Association for Computational Linguistics: IJCNLP-AACL 2026
Month:
November
Year:
2026
Address:
Hengqin, China
Editors:
Yue Zhang, Ruifeng Xu, Ayu Purwarianti, Tong Rong, Jun Suzuki
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
3144–3168
Language:
URL:
https://aclanthology.org/2026.findings-aacl.158/
DOI:
Bibkey:
Cite (ACL):
Tan-Minh Nguyen, Truong Dinh Do, Hiep K. V. Nguyen, and Le-Minh Nguyen. 2026. Copy Less, Ground More: Selective and Confidence-Aware Decoding for Grounded Legal Generation. In Findings of the Association for Computational Linguistics: IJCNLP-AACL 2026, pages 3144–3168, Hengqin, China. Association for Computational Linguistics.
Cite (Informal):
Copy Less, Ground More: Selective and Confidence-Aware Decoding for Grounded Legal Generation (Nguyen et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-aacl.158.pdf