Breaking Bureaucracy: Evaluating open-source LLMs for legal document review

Farrukh Baratov, Niki van Stein, Suzan Verberne


Abstract
In this paper, we evaluate open-source generative LLMs on legal Natural Language Inference (NLI). Legal inspectorial processes take place in specific domains and often deal with confidential data. This creates a need for working with local models that do not require labeled training data. We evaluate our models on the ContractNLI benchmark and two NLI4Wills datasets. We successfully reproduce the baseline for the task (Span NLI BERT) and we evaluate multiple open-source LLMs on the same task. We analyze the invalid rate of the models, and their stability across temperature settings and domains. Among the generative models, Gemma-4 26B performs the best, reaching an accuracy of 81.2%, even outperforming the supervised model on one metric. On accuracy, it is not possible to beat the supervised model with zero-shot approaches. Qwen-3.6 35B performs well on both ContractNLI and additional datasets in the legal wills domain. Our findings indicate that zero-shot, open-source, generative LLMs are a viable alternative for real-world legal NLI when no supervised data is available. Our code is available at [https://github.com/fbaratov/contractnli-llms](https://github.com/fbaratov/contractnli-llms).
Anthology ID:
2026.aacl-short.57
Volume:
Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 2: Short Papers)
Month:
November
Year:
2026
Address:
Hengqin, China
Editors:
Yue Zhang, Ruifeng Xu, Ayu Purwarianti, Tong Rong, Jun Suzuki
Venues:
AACL | IJCNLP
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
892–916
Language:
URL:
https://aclanthology.org/2026.aacl-short.57/
DOI:
Bibkey:
Cite (ACL):
Farrukh Baratov, Niki van Stein, and Suzan Verberne. 2026. Breaking Bureaucracy: Evaluating open-source LLMs for legal document review. In Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 2: Short Papers), pages 892–916, Hengqin, China. Association for Computational Linguistics.
Cite (Informal):
Breaking Bureaucracy: Evaluating open-source LLMs for legal document review (Baratov et al., AACL-IJCNLP 2026)
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PDF:
https://aclanthology.org/2026.aacl-short.57.pdf