The International Court of Justice (ICJ) could help stop the uncontrolled proliferation of satellites in Earth orbit, which threatens to erase stars from the sky, astronomers hope.
The initiative, spearheaded by the nonprofit Outer Space Institute, aims to lobby the United Nations to request an advisory opinion from the ICJ, the UN's principal judicial body. Through this, scientists want to gain clarity over the legal responsibilities of launching states to preserve near-Earth space from orbital clutter and the dark night sky from excessive light pollution.
The campaign, originally conceived in 2023 to address the impact of internet-beaming megaconstellations like SpaceX's Starlink, has taken on new urgency over the past 12 months. The escalation comes as tech giants and aerospace firms — including SpaceX, Google and Starcloud — have announced plans to deploy unprecedented networks of hundreds of thousands of space-based data centers.
Furthermore, in July, the U.S. Federal Communications Commission (FCC) granted a license to California-based Reflect Orbital to fly a demonstrator space mirror, called Eärendil-1. Scheduled to launch later this year, the satellite is the first step toward a possible future constellation of tens of thousands of such mirrors, which would reflect sunlight to photovoltaic plants on Earth after sunset. If those plans were to pass, the fleet could brighten the night sky so much that astronomical observations around the world might become impossible, critics say.
Aaron Boley, an astronomer at the University of British Columbia and co-director of the Outer Space Institute, told Space.com that the initiative was spurred by the failure to gain unanimous approval from the UN Committee on the Peaceful Uses of Outer Space (COPUOS) to set up an expert group to monitor light pollution.
"Getting stuff through COPUOS can be very, very difficult because COPUOS works through consensus," Boley said. "Consensus is very hard to achieve, and so you get a lot of stalled initiatives."
The committee negotiates rules for international collaboration in space, but the requirement for unanimous agreement means conflicting national interests frequently stand in the way.
With the ICJ, Boley added, the path may be smoother and faster. A single nation could put a resolution forward to the UN General Assembly to request the ICJ's advisory opinion. With the support of a simple majority of the states present and voting, the request is then passed to the court.
"You only need 50% plus one of the voting states," said Boley. "So that's very hard for a single state to block. If, for whatever political reasons, a state feels like it cannot vote, they still cannot stop it."
The court then reviews the presented evidence and issues an opinion regarding the interpretation of an international treaty or ambiguous piece of law. There is, however, a catch.
"The ICJ has no enforcement mechanism, so the opinions are more of a diplomatic tool," Robin J. Frank, an international law and policy expert and a former legal counsel at NASA, told Space.com. "But it can still be very valuable. It helps to raise awareness of the issue, gives like-minded countries an opportunity to cooperate and carries a certain moral authority. In the end, a state's self-interest is usually best served by its abiding by international standards."
Boley pointed out the case championed by the tiny South Pacific island nation of Vanuatu, which in 2023 gained substantial international backing to obtain the court's opinion about nations' obligations to combat climate change. The ensuing advisory opinion, issued in July 2025, firmly stated that states must take action to prevent climate-related damage to vulnerable nations and future generations or face legal consequences. The UN General Assembly adopted a resolution based on the opinion in May 2026.
The opinion has since helped climate change activists worldwide boost their cases in local courts. For example, environmental campaign groups recently requested that a Paris court order the French oil giant TotalEnergies to disclose the climate risks related to its oil and gas production. Their argument, which relied on the Vanuatu advisory opinion, was successful; this past June, the court ruled that TotalEnergies must make such disclosures
"Even though it's not legally binding, the ICJ's advisory opinion comes with incredible authority," Boley says. "One could, for example, use it to actually bring forward a dispute."
Frank agreed. She said that, if dark-sky activists in the U.S., for example, wanted to mount a legal case against the FCC for disregarding environmental impacts of satellite megaconstellation projects, the ICJ's advisory opinion would come in handy.
"Using the ICJ advisory opinion in domestic judicial proceedings has a substantial weight," she said. "It might help sway the local courts to, essentially, comply with it. It can have a significant impact."
She added that the opinion issued in the Vanuatu case signals that the ICJ takes environmental issues seriously, providing a glimmer of hope to the astronomers.
The scientists would request the ICJ to clarify aspects of the 1967 Outer Space Treaty, which provides the backbone of international space law, said Boley. The Treaty's Article 9 sets out the concept of due regard, which means that, although nations are free to explore space, they must do that while respecting the activities and interests of other nations.
"The ICJ won't tell the U.S. how many satellites it can or cannot launch," said Boley. "But down the road, it can change how the U.S. approaches satellite licensing in general."
He added that astronomers have long been trying to engage with satellite megaconstellation operators and government bodies to raise awareness of the problem. So far, he said, they have not achieved the outcome they want.
The earlier attempt to set up an expert group within UN COPUOS to monitor satellite light pollution and impacts on astronomy was backed by Chile, Spain, Slovakia, Bulgaria, the Dominican Republic, Peru and South Africa.
