Watermarking Large Language Models in Europe: Interpreting the AI Act in Light of Technology

TL;DR

This paper analyzes how European AI regulations impact LLM watermarking, proposing a taxonomy, evaluation framework, and comparison of methods to ensure compliance with reliability, robustness, and interoperability standards.

Contribution

It introduces a comprehensive taxonomy and evaluation framework for LLM watermarking aligned with European AI Act requirements, highlighting gaps and future research directions.

Findings

No current watermarking method meets all EU standards.

Proposed normative dimensions for assessing watermark interoperability.

Encourages embedding watermarks within LLM architectures.

Abstract

To foster trustworthy Artificial Intelligence (AI) within the European Union, the AI Act requires providers to mark and detect the outputs of their general-purpose models. The Article 50 and Recital 133 call for marking methods that are ''sufficiently reliable, interoperable, effective and robust''. Yet, the rapidly evolving and heterogeneous landscape of watermarks for Large Language Models (LLMs) makes it difficult to determine how these four standards can be translated into concrete and measurable evaluations. Our paper addresses this challenge, anchoring the normativity of European requirements in the multiplicity of watermarking techniques. Introducing clear and distinct concepts on LLM watermarking, our contribution is threefold. (1) Watermarking Categorisation: We propose an accessible taxonomy of watermarking methods according to the stage of the LLM lifecycle at which they are applied - before, during, or after training, and during next-token distribution or sampling. (2) Watermarking Evaluation: We interpret the EU AI Act's requirements by mapping each criterion with state-of-the-art evaluations on robustness and detectability of the watermark, and of quality of the LLM. Since interoperability remains largely untheorised in LLM watermarking research, we propose three normative dimensions to frame its assessment. (3) Watermarking Comparison: We compare current watermarking methods for LLMs against the operationalised European criteria and show that no approach yet satisfies all four standards. Encouraged by emerging empirical tests, we recommend further research into watermarking directly embedded within the low-level architecture of LLMs.