Satellites Can Spot Illegal Fishing, but Vague Laws Let It Slide

Satellites circling the planet can now watch the ocean with astonishing precision. They can identify a fishing vessel, fix its position, timestamp its movement, and track its course through waters where no fishing should be happening at all. Yet a sweeping new analysis of marine protected area legislation reveals a startling disconnect: the technology has outrun the law. In most of the world’s marine protected areas, the rules are written in language so vague, so discretionary, and so detached from the kinds of evidence satellites produce that even a perfect detection of illegal fishing may be legally useless. The study, published in npj Ocean Sustainability, examined nearly ten thousand protected zones across fifteen countries and found that the regulatory architecture of ocean protection is fundamentally unprepared for the satellite era.

The research team, led by Fabio Favoretto of the University of Plymouth alongside colleagues from institutions including the Scripps Institution of Oceanography, ProtectedSeas, and the National Geographic Society’s Pristine Seas program, set out to answer a deceptively simple question. If a satellite detects a vessel fishing inside a marine protected area, can that observation actually support an enforcement action? The answer, they found, depends almost entirely on how the law is written. Remote detection can establish a vessel’s identity, its position, the time, and its movement. What it cannot do, on its own, is prove that the activity was prohibited in terms the law recognizes. That gap between what satellites can see and what regulations can prove is the central finding of the study.

To quantify that gap, the researchers built what they call a Regulation Preparedness Index, a scoring system that measures whether the text of a protected area’s rules can be matched by remote evidence. They analyzed the regulatory language of 9,740 marine protected area zones and 119 national legal instruments across fifteen countries. The results were sobering. The mean score for protected area rules was just 33 out of 100. In other words, the average protected zone on Earth is governed by regulations that satellite evidence can rarely support. Sixty-one percent of the zones contained discretionary language, phrasing that gives officials or courts room to interpret whether an activity was actually forbidden. Only four percent of zones referred to vessel monitoring systems or satellite technology at all, meaning the vast majority of the world’s protected areas never contemplated remote detection as a source of proof.

Discretionary language deserves particular attention, because it is where satellite evidence most often dies in the legal system. A rule that says fishing ‘may be restricted’ or that certain activities ‘should be avoided’ is not the same as a rule that says fishing is prohibited. When a patrol boat intercepts a trawler, an officer can gather testimony, inspect the catch, and document gear. When a satellite flags a vessel, all it has is a track. If the regulation requires proof of intent, or if it hedges the prohibition with exceptions and qualifications, the track may not be enough. The study found that this kind of hedged, conditional drafting is the norm rather than the exception across the protected zones it examined, leaving enforcement authorities with detections they cannot convert into cases.

The problem does not stop at the boundaries of individual protected areas. The researchers also screened national legislation for the provisions that determine whether satellite evidence can travel through the legal system: evidentiary rules that say what kinds of data courts will accept, penalty provisions that attach consequences to specific violations, enforcement powers that let authorities act on remote detections, technology frameworks that formally recognize satellite monitoring, and liability rules that assign responsibility to vessel owners and operators. Here the mean score across the fifteen countries was 47 out of 100, better than the zone-level scores but still far from adequate. Crucially, no country in the analysis scored above 50 on both layers simultaneously. Even the nations with the strongest national frameworks fail to pair them with protected area rules that remote evidence can actually prove.

This mismatch has consequences for one of the most ambitious commitments in environmental history. The international community has pledged to protect thirty percent of the ocean by 2030, a target that has driven a rapid expansion of marine protected areas around the world. Area-based protection without enforcement, however, risks becoming protection on paper only. Satellite monitoring promised to close the enforcement gap at near-global scale, offering a way to watch vast, remote expanses of ocean that no patrol fleet could ever cover. The new findings suggest that promise is being strangled not by technology or by cost but by drafting choices made decades ago, or made today, in legal texts that were never written with remote sensing in mind.

The good news, and it is genuinely good, is that the fix requires no new satellites, no new sensors, and no new science. The researchers modeled what would happen if protected area rules were rewritten as spatially explicit, unconditional prohibitions, paired with vessel-tracking and reporting obligations. Under that scenario, the mean Regulation Preparedness Index more than doubled, rising from 33 to 76. The authors are careful to describe this figure as an index-internal upper bound, a theoretical ceiling that assumes every zone adopts the full package of satellite-ready drafting elements. Reaching it would require formal amendment of existing regulations, which is a political and administrative undertaking, but not a technological one. The tools to watch the ocean already exist; the words to act on what they see do not.

The study lays out those drafting elements in detail, offering what amounts to a template for lawmakers. Rules should be spatially explicit, meaning the boundaries of the prohibited area are precisely defined in coordinates that a satellite track can be checked against. Prohibitions should be unconditional, stripped of the discretionary hedges that give violators room to argue. Regulations should impose vessel-tracking obligations, so that ships operating near or inside protected areas carry the transponders that make them visible, and reporting obligations, so that their presence is documented. And national legislation should formally recognize satellite and monitoring data as evidence, so that a detection made in orbit can survive the journey to a courtroom. None of these elements is exotic; all of them are drafting decisions.

The stakes extend well beyond coastal waters. A new high seas treaty, agreed under the United Nations Convention on the Law of the Sea, is poised to create protected areas in ocean territory that lies beyond any single nation’s jurisdiction. On the high seas, where no coast guard routinely patrols, satellite monitoring will not merely supplement enforcement; it will be the primary means of knowing whether the rules are being followed at all. The authors explicitly frame their findings as relevant to the design of these future high seas protections, arguing that the drafting lessons from coastal zones should be applied from the outset rather than retrofitted after the fact. If the treaty’s protected areas are written in the same discretionary language that pervades existing zones, the same enforcement gap will be exported to the largest unprotected portion of the planet.

What emerges from this research is a reframing of the ocean conservation debate. The conversation has long focused on how much ocean to protect and where, and satellite technology has been celebrated as the eyes that will keep watch over it all. This study shifts attention to a quieter, more technical, and arguably more decisive question: whether the words in the regulations can be matched by the data from the sky. With a mean preparedness score of 33 out of 100 across nearly ten thousand zones, and no country strong on both the zone and national levels, the answer today is mostly no. The path to yes is mapped, costed in legal effort rather than hardware, and available to any government willing to rewrite its rules in terms a satellite can prove.

Subject of Research: The compatibility of marine protected area regulations with satellite-based enforcement evidence

Article Title: Regulatory language limits satellite-based enforcement in marine protected areas

Article References: Favoretto, F., López-Sagástegui, C., Guidetti, P., Simone, A., Sletten, J., Zetterlind, V., Aburto-Oropeza, O., Fraser, K., & Sala, E. (2026). Regulatory language limits satellite-based enforcement in marine protected areas. npj Ocean Sustainability. https://doi.org/10.1038/s44183-026-00251-9

Image Credits: AI Generated

DOI: 10.1038/s44183-026-00251-9

Keywords: marine protected areas, satellite monitoring, ocean enforcement, regulation preparedness index, illegal fishing, vessel tracking, high seas treaty, ocean governance, remote sensing, 30 by 30, environmental law, npj Ocean Sustainability