Platform Liability as an Implied Publisher in Online Defamation on Social Media

Abstract

This study aimed to analyze the tortious liability of platform service providers as “implied publishers” in online defamation cases under both Thai and comparative legal systems, and emphasized the application of civil-law principles governing tort liability under Sections 420 and 432 of the Thai Civil and Commercial Code, together with Section 15 of the Computer Crime Act B.E. 2560 (2017), a key provision regulating the liability of online intermediaries in the digital environment.

The results indicated that the Thai legal framework needed a coherent mechanism linking platform liability to the principle of fault-based liability. Furthermore, Section 15 of the Computer Crime Act functioned primarily as a criminal provision that imposed liability on service providers without requiring proof of intent or negligence. This approach contradicted the civil-law concept of fault-based liability and produced an imbalance between protection of an individual’s reputation and preservation of freedom of expression in the public sphere.

From a comparative perspective, the United States adopted an absolute-immunity model under Section 230 of the Communications Decency Act which, while promoting freedom of speech, granted overly broad immunity that weakened platform accountability. The European Union applied a conditional safe-harbour model under the E‑Commerce Directive and the Digital Services Act (DSA), establishing a notice-and-takedown mechanism as a condition for exemption from liability. In contrast, Australia developed the doctrine of the “implied publisher” through landmark decisions such as Fairfax Media Publications v Voller and Google LLC v Defteros, which distinguished between active and passive conduct by platforms in line with tort-law principles.

To address these gaps, this study proposed a Hybrid Liability–Defense Model that integrated the implied-publisher principle with a due-care defense mechanism, following the conditional safe-harbour approach. The hybrid framework aimed to balance the right to reputation and freedom of expression, consistent with the principle of proportionality enshrined in the Constitution of the Kingdom of Thailand B.E. 2560 (2017) and with international human rights standards.