Mitigating Legal Hallucinations via Symbolic Constraints and Analogical Precedents

Zixuan Huang, Yanxiang Ma, Luhan Wang, Yunke Wang, Duo Shi, Chang Xu


Abstract
With the growing potential of large language models (LLMs) in the legal domain, domain-specific finetuning and retrieval-augmented generation (RAG) methods have received widespread attention. However, current methods still suffer from hallucination risk and failing to resolve semantic drift and adapt to varying citation numbers. To address this, we propose Authoritative and Accurate Lawyer (AALawyer), a complementary dual-retriever framework based on the Legal Syllogism and the nature of different legal data. First, we introduce Symbolic Constrained Retrieval (SCR) for closed-set article retrieval, by constraining retrieval to the generative prediction. Second, we build Analogical Precedent Retrieval (APR) to retrieve open-set judicial precedents for reasoning with a newly collected large criminal dataset.Extensive experiments, including LawBench, our Hallucination Risk-Benchmark, and comprehensive ablation studies, demonstrate the effectiveness of AALawyer, which mitigates hallucinations while improving the explainability of legal reasoning.
Anthology ID:
2026.acl-long.633
Volume:
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Month:
July
Year:
2026
Address:
San Diego, California, United States
Editors:
Maria Liakata, Viviane P. Moreira, Jiajun Zhang, David Jurgens
Venue:
ACL
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Publisher:
Association for Computational Linguistics
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Pages:
13894–13920
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URL:
https://preview.aclanthology.org/ingest-acl/2026.acl-long.633/
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Cite (ACL):
Zixuan Huang, Yanxiang Ma, Luhan Wang, Yunke Wang, Duo Shi, and Chang Xu. 2026. Mitigating Legal Hallucinations via Symbolic Constraints and Analogical Precedents. In Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers), pages 13894–13920, San Diego, California, United States. Association for Computational Linguistics.
Cite (Informal):
Mitigating Legal Hallucinations via Symbolic Constraints and Analogical Precedents (Huang et al., ACL 2026)
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https://preview.aclanthology.org/ingest-acl/2026.acl-long.633.pdf
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