Rendering Data Unlearnable by Exploiting LLM Alignment Mechanisms

Ruihan Zhang, Jun Sun


Abstract
Large language models (LLMs) are increasingly trained on massive, heterogeneous text corpora, raising serious concerns about the unauthorised use of proprietary or personal data during model training. In this work, we address the problem of data protection against unwanted model learning in a realistic black-box setting. We propose Disclaimer Injection, a novel data-level defence that renders text unlearnable to LLMs. Rather than relying on model-side controls or explicit data removal, our approach exploits the models’ own alignment mechanisms: by injecting carefully designed alignment-triggering disclaimers to prevent effective learning. Through layer-wise analysis, we find that fine-tuning on such protected data induces persistent activation of alignment-related layers, causing alignment constraints to override task learning even on common inputs. Consequently, models trained on such data exhibit substantial and systematic performance degradation compared to standard fine-tuning. Our results identify alignment behaviour as a previously unexplored lever for data protection and, to our knowledge, present the first practical method for restricting data learnability at LLM scale without requiring access to or modification of the training pipeline.
Anthology ID:
2026.acl-long.1885
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
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
40587–40598
Language:
URL:
https://preview.aclanthology.org/ingest-acl/2026.acl-long.1885/
DOI:
Bibkey:
Cite (ACL):
Ruihan Zhang and Jun Sun. 2026. Rendering Data Unlearnable by Exploiting LLM Alignment Mechanisms. In Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers), pages 40587–40598, San Diego, California, United States. Association for Computational Linguistics.
Cite (Informal):
Rendering Data Unlearnable by Exploiting LLM Alignment Mechanisms (Zhang & Sun, ACL 2026)
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https://preview.aclanthology.org/ingest-acl/2026.acl-long.1885.pdf
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