IN 2015 Congress passed a law to legalise mining in outer space—the first of its kind in the world. Firms that some day manage to mine asteroids for resources like water or precious metals would henceforth be allowed to own, process, and sell anything harvested. The nascent space-mining industry was thrilled. The boss of a firm called Planetary Resources compared it to the Homestead Act of 1862—a law that gave up to 160 acres in the American West to any plucky settler willing to venture forth. More recently Wilbur Ross, the commerce secretary, has talked about creating a more “permissive” regulatory environment in space and turning the moon into a “gas station” for further exploration. Other countries are following suit: Luxembourg passed a similar measure last year and earmarked €200m to invest in space-mining companies. But not everyone is pleased. At the UN committee dealing with outer space, Russia condemned the American move, citing America’s “total disrespect” for international law. Critics say America is conferring rights that it has no authority to confer. There are indeed legal grey areas. Who owns what in outer space?

Space is a commons. That was determined in the 1950s by a UN committee, and laid out a decade later in the Outer Space Treaty. No country can lay claim to the moon, asteroids or other celestial bodies; space is open to all for exploration. The language of early treaties is notably grand, with space referred to as the “province of all mankind”. Reality has been far more fraught. In 1957 the Soviet Union launched Sputnik, Earth’s first artificial satellite. The achievement heightened American anxieties that nuclear tensions could spill over and upwards. Both countries determined to protect outer space from nuclear confrontation by enshrining the principle of peaceful use.

A nuclear standoff in space is no longer the foremost concern. At issue now is commercial activity, as private firms—rather than nation states—look to space for profit. Developed in the 1950s and ’60s, space law is state-centric and arguably ill-suited to a commercial future. The legal status of resources mined in space remains ambiguous, and industry wants clarification. The laws adopted by America and Luxembourg were first steps in that direction. But national law will only protect firms from competing claims by their compatriots, notes Tanja Masson-Zwaan, a space-law expert. A Chinese company will not be bound by American law. “It’s in everybody’s interest to have some kind of international governance system,” she adds. One analogy is the high seas, where an International Seabed Authority grants licences for drilling. Another less likely model is Antarctica, where mining was banned under international agreement for 50 years, from 1998.

Does any of this matter? The market for asteroid minerals is currently nonexistent. But that is likely to change, as technical hurdles diminish and commercial activity—such as space tourism—develops. Planetary Resources and Deep Space Industries, another firm, plan to launch prospecting missions by 2020. One idea is to extract water from asteroids and break it down into hydrogen and oxygen to refuel rockets in space. That is far cheaper than transporting fuel from Earth and will permit longer flights with heavier payloads. Asteroid mining looks to be at least decades away. Expect a land grab when it comes.