Europe Just Weaponized Consent: GDPR Enforcement Just Turned into Global AI Leverage

On May 14, 2025, the Belgian Market Court delivered a landmark ruling that may redefine how personal data powers both digital advertising and AI model training. Building on the March 2024 CJEU judgment (Case C-604/22), the court confirmed that “Transparency and Consent Strings” (TC Strings), those codes embedded in cookie pop-ups generated through IAB Europe’s Transparency and Consent Framework (TCF), are personal data under GDPR.

And IAB Europe is now officially a joint controller in the creation and storage of their data.

This isn't a niche ruling. It's a shot across the bow at the core data infrastructure AI systems rely on today.

What Actually Happened?

Consent strings = personal data.

When linked to a user, these identifiers are shared with hundreds of third parties, including entities operating far outside European jurisdiction, such as in the United States, China, and Russia. In many cases, this occurred without proper safeguards or meaningful user consent.

The €250,000 penalty from the Belgian DPA stands, and TC Strings are now fully regulated as personal data.

The €250,000 penalty from the Belgian DPA was upheld, along with findings of GDPR violations. These consent signals, long treated as harmless metadata, are now regulated like real personal data.

Why It Blows Open the AI Question

This isn’t just an AdTech compliance story.
It hits at the industrial-scale data pipelines feeding today’s AI training ecosystems.

Meta recently claimed it could train its models on Facebook and Instagram data without user opt-in, citing “legitimate interest.”

This ruling makes that strategy legally brittle, if not untenable.

And it’s not just Meta. The same legal logic applies to every ecosystem running silent data capture at scale:

• Microsoft: telemetry from apps and OS behavior
• Google: cross-product tracking (Search, YouTube, Maps, Android)
• Amazon: clickstream data, Alexa inputs, purchase behavior

These are not side streams. They are foundational inputs for personalization engines and AI model training.

Under this ruling, the assumption that these signals are “fair game” is no longer safe.

The Collapse of ‘Legitimate Interest’

For over a decade, “legitimate interest” has been the go-to legal fallback in EU privacy law. It allowed companies to collect and process personal data without explicit opt-in, as long as they could argue it was reasonably necessary, and users weren’t significantly impacted.

That argument is now collapsing under legal pressure.

The Belgian ruling makes it clear: when data like TC Strings can be linked to an individual and used for high-impact profiling or model training, blanket justifications are not enough.

“Legitimate interest” is no longer a shield. It’s a stress test.

• It removes the legal grey zone many AI and AdTech companies have exploited.
• It shifts the burden of proof. Companies now need to demonstrate a rights-based, accountable justification, not just cite boilerplate clauses.
• It may force retraining, redaction, or segmentation of AI models built on improperly sourced data.

The Bigger Strategic Play: Consent as Infrastructure

Zoom out. This ruling isn’t just about compliance. It is about who gets to shape the future of AI infrastructure.

Consent, in this context, becomes more than a privacy right. It becomes a governance tool that defines how knowledge economies are built, who benefits from user data, and what global systems must adapt to local law.

This is about digital sovereignty: the ability of a region to assert control over how its citizens’ data is extracted, processed, and transformed into value.

And in the AI age, that means:

• Influencing global training standards
• Triggering architectural changes in model pipelines
• Forcing infrastructure localization for compliance

For Founders, Operators, and Policy Teams

• Audit your consent logic. Is it real, or banner theatre?
• Review every training input. Is it backed by clear, user-granted rights?
• Rethink reliance on “legitimate interest”.
• Watch for regional AI pipelines becoming the norm: local data, local rules.

While the immediate impact is on AdTech and AI, any industry relying on large-scale behavioural data, such as FinTech, HealthTech or mobility platforms, should pay close attention to how consent and personal data are defined going forward.

What’s Next?

The Belgian Market Court’s decision may prompt further appeals or clarifications from EU regulators.

The European Data Protection Board (EDPB) may issue guidance to harmonize how this ruling is applied across member states. This could raise the compliance bar for all companies handling behavioural data in AI and beyond.

The debate over “legitimate interest” as a legal basis is far from over. But the trajectory is clear: accountability is rising, and the margin for ambiguity is shrinking.

Europe didn’t just rule on cookies.

It just redrew the legality map for AI training, with consent as its new border control.