The Constitutional Court Upholds the “Nth Room Prevention Act” — A Troubling Decision

Mandatory Upload Filtering Must Not Become a Gateway to Institutionalized Online Censorship

If all video uploads are screened against administrative standards before publication, the system amounts to prior censorship

On October 23, 2025, the Constitutional Court of Korea upheld the constitutionality of Article 22-5(2) of the Telecommunications Business Act, which imposes on certain value-added telecommunications service providers designated by Presidential Decree an obligation to implement technical and administrative measures — including mandatory upload filtering — to prevent the distribution of unlawfully filmed intimate content (Constitutional Court Decision 2021Hun-ma290, Oct. 23, 2025). This decision is deeply concerning because it effectively legitimizes a system under which the government imposes mandatory prior filtering obligations on online platforms, thereby creating a serious risk of infringing internet users’ freedom of expression and freedom of communication.

Article 22-5(2) of the Telecommunications Business Act — enacted in 2020 during the final days of the 20th National Assembly under the name of the so-called “Nth Room Prevention Act” — requires certain value-added telecommunications service providers designated by Presidential Decree (hereinafter “providers subject to prior-measure obligations”) to implement “technical and administrative measures prescribed by Presidential Decree” (hereinafter “prior measures”) in order to prevent the distribution of unlawfully filmed intimate content. Failure to comply is punishable by up to three years’ imprisonment or a criminal fine of up to KRW 100 million (Article 92-2(1)3 of the same Act).

Under the Enforcement Decree adopted pursuant to this provision, “providers subject to prior-measure obligations” include webhard service providers and value-added telecommunications service providers operating social media platforms, online communities, chat rooms, personal streaming services, and search services with annual revenue exceeding KRW 1 billion or an average of more than 100,000 daily users. The required “prior measures” include: establishing reporting mechanisms; measures to identify and restrict searches for unlawfully filmed intimate content; measures restricting uploads; and advance warning measures (Enforcement Decree Article 30-6(1), (2)).

The Constitutional Court first held that delegating the designation of covered service providers and the content of the required prior measures to Presidential Decree did not violate the constitutional prohibition on overly broad delegation, reasoning that the delegated matters were sufficiently foreseeable and that flexibility was necessary in order to respond to technological developments. The Court also held that phrases such as “a person’s body capable of provoking sexual desire or humiliation,” contained within the statutory definition of unlawfully filmed intimate content, did not violate the constitutional principle of clarity.

The most significant aspect of the decision concerns whether the obligation to implement “measures to identify and restrict the posting” of unlawfully filmed intimate content — commonly referred to as mandatory upload filtering — violates the constitutional prohibition on prior censorship and the principle of proportionality.

The Court reasoned that these measures merely “mechanically compare hash values in order to prevent the further distribution through information and communications networks of content that has already been collected by the Korea Communications Standards Commission (KCSC) and determined to constitute unlawfully filmed intimate content.” Accordingly, the Court concluded that the measures do not constitute unconstitutional prior censorship because they do not involve “administrative authorities substantively reviewing or screening ideas or opinions before publication for the purpose of suppressing expression in advance.”

The Court also acknowledged that “users are subject to the constraint of having the content they wish to post reviewed,” and that “as a result of the prior-measure obligations, users may have their searches or postings restricted and may experience disadvantages such as a chilling effect on their freedom of communication and freedom of expression through the process of verifying the hash values of content they seek to upload.” Nevertheless, the Court concluded that the measures do not violate the principle of proportionality because the law “requires analysis of the characteristics of content a user seeks to post and comparison and identification of whether it corresponds to content determined by the KCSC to constitute unlawfully filmed intimate content,” thereby employing “a comparative recognition technique based on the comparison of hash values.” The Court emphasized that “only the hash values of information are compared through technical means,” and that the system “does not enable providers subject to prior-measure obligations or relevant authorities to directly inspect or monitor the actual substance of content users seek to post.”

However, a system that examines whether content users seek to upload corresponds to content designated as illegal by an administrative body such as the KCSC, and that preemptively blocks its publication, constitutes prior censorship in a broad constitutional sense. The Court appears to have reasoned that because the content at issue had already once been publicly available, and because the system merely prevents its redistribution through technical means, it differs from traditional prior censorship that blocks access to expression before it enters the marketplace of ideas.

Yet the Court overlooks a critical point: even lawful videos and lawful information are subjected to prior administrative determination before publication is permitted. Prior censorship does not exist only where specific expression is ultimately prohibited. A system under which publication itself depends upon administrative approval or review is itself constitutionally suspect.

Even if the system merely compares hash values through technical means, this is simply the automation and mechanization of what would otherwise be human review. Moreover, hash values themselves are derived from and represent the substance of the content being analyzed. The law effectively requires internet intermediaries to extract and process digitally encoded characteristics of the expression users seek to distribute, compare them against digital codes reflecting government-designated review standards, and determine whether distribution should be permitted.

In substance, the law compels internet platforms to carry out censorship on behalf of administrative authorities. The only difference is that content review is conducted through automated technical systems rather than through direct human inspection.

Once such a system is legitimized, mandatory upload filtering could easily expand beyond unlawfully filmed intimate content to encompass all forms of allegedly unlawful information, including copyright-infringing materials and allegedly subversive expression. The ultimate result would be the normalization of a prior censorship regime in which the permissibility of online expression is determined not by the judiciary but by administrative bodies such as the KCSC or its successor agencies.

Moreover, for such filtering systems to function, internet platforms must necessarily be equipped with systems capable of inspecting what users intend to post before publication — that is, systems capable of monitoring user communications prior to posting. Such systems inevitably and severely undermine the secrecy and freedom of communication, as well as freedom of expression.

This concern is especially serious given that the KCSC’s review standards are defined in extraordinarily vague terms such as “necessary for the establishment of sound communications ethics.” Even if narrowed by subordinate regulations, these standards clearly extend beyond unlawful content to encompass merely “harmful” information, making them far too indeterminate to serve as constitutionally adequate standards for mandatory upload filtering.

The Constitutional Court appears to have justified these preventive measures in light of the particularly severe harm unlawfully filmed intimate content inflicts upon victims’ dignity and personal rights. The devastating impact of such content and the importance of efforts to combat it cannot be overstated. Nevertheless, institutionalizing systems of internet content filtering and censorship requires the utmost caution because such systems have profound implications not only for internet governance and the online environment as a whole, but also for the fundamental rights of ordinary citizens.

Open Net hopes that this decision will not become a catalyst for expanding mandatory upload filtering systems to other categories of allegedly unlawful information, and urges the legislature to establish a framework for addressing illegal online content that remains compatible with freedom of expression and freedom of communication.