How have other jurisdictions (EU, Germany, US) regulated or litigated mandatory client‑side scanning proposals and what were the outcomes?
Executive summary
Mandatory client‑side scanning has been fought, stalled, and reworked across jurisdictions: the EU’s “Chat Control”/CSAR proposals provoked a major political and legal backlash that forced governments to pare back mandatory scanning and consider voluntary or narrow alternatives [1] [2] [3], Germany emerged as a decisive opponent that blocked a mandatory path and invoked constitutional and proportionality arguments [4] [2], while U.S. and allied technical and civil‑society actors have framed client‑side scanning as a structural security risk even where governments push for tools to detect CSAM [5] [6]. The net outcome so far is delay, narrowed scopes, and heavy scrutiny — not a settled legal precedent requiring device‑level, universal scanning.
1. EU politics: from mandatory detection orders to a stalemate
Brussels’ 2022 CSAR draft sought to move from voluntary detection to mandatory obligations that could reach end‑to‑end encrypted services via “detection orders,” provoking a split among member states and a fierce public campaign that left the regulation debated but not enacted in its original form [1] [7] [8]. By mid‑2025 political arithmetic shifted repeatedly: some member states backed mandatory scanning, others refused, and Parliament had already adopted a more privacy‑protective text — forcing trilogue bargaining rather than rapid implementation [8] [3]. Under Danish presidency pressure to resolve the deadlock, mandatory detection requirements were at times reintroduced and then pulled back; in late 2025 Denmark announced it would drop mandatory scanning from its compromise after Germany’s opposition created a blocking minority, effectively leaving voluntary frameworks in place until at least 2026 [2] [9].
2. Germany: legal posture, political leverage, and claims of disproportionality
Germany’s role has been pivotal: privacy advocates and some German institutions argued client‑side scanning would breach proportionality and fundamental rights, pointing to prior rulings such as the German Constitutional Court’s rejection of broad data retention as precedent for legal challenge [4] [10]. Political resistance in Berlin translated into practical blocking power — Germany’s refusal to support mandatory scanning stalled a Council vote and forced Denmark to change course in 2025 [2] [3]. German critics also highlighted practical failings — for example official data suggesting high false‑positive rates in existing reporting that would swamp enforcement — to argue the measure is ineffective as well as unconstitutional [11] [10].
3. Civil‑society, technical and industry pushback: security and rights arguments
Cryptographers, privacy NGOs and major secure‑messaging projects framed client‑side scanning as an attack on end‑to‑end encryption and a creator of systemic security vulnerabilities, arguing that any mechanism that inspects content on devices creates permanent attack surfaces and undermines anonymous communication [6] [12] [5]. Signal and EFF warned of withdrawal or legal challenges if firms were forced to compromise encryption, and technical communities (IETF/IAB signatories) explicitly opposed mandatory client‑side scanning on architectural and safety grounds [13] [5]. Those objections helped mobilise public campaigns and informed parliamentary amendments toward narrower proposals [3] [12].
4. Proponents’ case and contested evidence on effectiveness
Advocates of stronger detection argue the policy is aimed at protecting children and that automated detection — especially for known CSAM hashes — already produces substantial leads for law enforcement, a rationale driving several member states’ support [14] [3]. Yet critics point to evidence of large volumes of irrelevant or false reports and warn that expanding scanning would overload authorities and raise serious rights costs; Germany’s own figures and civil‑society analyses were repeatedly cited to question efficacy [11] [10]. The debate therefore hinges not only on legality but on contested empirical claims about detection accuracy, proportionality and whether voluntary/targeted tools can deliver comparable protection without systemic scanning [8] [7].
5. The U.S. scene and litigation: technical opposition, limited legal closure
U.S. coverage in the reporting is mainly about technical and standards‑body resistance rather than a mature body of binding court precedents: industry and standards groups warned against export of mandatory client‑side scanning designs and flagged cross‑border technical harms, while commentators and civil‑society entities pressed U.S. policymakers to avoid regulatory paths that would require device‑level inspection [5] [6]. The sources do not document a final U.S. judicial decision that squarely resolved mandatory client‑side scanning, so outcomes there remain shaped by policy debate, industry choice, and technical community norms rather than settled litigation accessible in the provided reporting [5].
6. Bottom line: delay, narrowing and legal uncertainty
Across the EU and Germany the immediate legal and political outcome has been postponement and narrowing: mandatory universal client‑side scanning has been blocked or paused, voluntary or more limited measures are in force or under negotiation, and strong legal challenges based on proportionality and encryption rights are anticipated — but no definitive, transnational legal precedent that authorises universal client‑side scanning has been established in the provided reporting [2] [4] [12]. The U.S. debate remains influential for technical norms but lacks a decisive litigation endpoint in these sources [5].