In the event of an extinction-level asteroid heading toward Earth, current international law could prevent nations from using nuclear weapons to deflect it—a legal gap that a prominent legal scholar says should be addressed before a crisis emerges. James Green, a professor of public international law, argues that the time to prepare is now, not when an asteroid is on a collision course.
Green's proposal, published in The Conversation, calls for a new international agreement that would explicitly permit the use of nuclear devices against incoming celestial threats. He points to the Outer Space Treaty of 1967, which prohibits the placement of nuclear weapons in orbit or on celestial bodies, as a major obstacle. While the treaty was designed to prevent the militarization of space, it also inadvertently blocks a potential planetary defense mechanism.
The urgency is underscored by past statements from Russia and the European Union, both of which have indicated willingness to launch nuclear strikes against threatening asteroids, according to a 2016 Telegraph report. However, without a clear legal framework, such actions could be misinterpreted as acts of aggression, potentially escalating into international conflict.
Why a Pre-Agreed Framework Is Critical
Green emphasizes that waiting until an asteroid is detected to negotiate rules would be disastrous. "All of this would be extremely complex (legally, politically and financially) and would take a huge amount of time to set up," he writes. "But when it comes to the 'asteroid threat', time is not an issue. Until it is. So I suggest we get started now."
The professor suggests that a new governing body be established to oversee any nuclear launch, ensuring that no nation exploits the situation for military advantage. This body would set protocols for when and how a nuclear device could be deployed, and would provide a clear chain of command to avoid miscommunication.
The idea is not without precedent; scientists have long considered nuclear detonation as a viable method to deflect or destroy an asteroid, though it remains a last-resort option. Other strategies, such as kinetic impactors or gravity tractors, are less destructive but may be insufficient for larger objects.
Green's call comes amid growing international interest in planetary defense. NASA's DART mission, which successfully altered an asteroid's orbit in 2022, demonstrated that kinetic deflection is possible, but nuclear options may still be necessary for the largest threats.
The legal hurdles are significant. Any new treaty would require consensus among spacefaring nations, and the political will to prioritize a hypothetical scenario over immediate concerns. Yet Green argues that the cost of inaction is too high: without a pre-agreed framework, humanity might face an avoidable catastrophe.
While the proposal is likely to spark debate among legal and military experts, it highlights a critical gap in current space governance. As asteroid detection improves, the question of how to respond to a genuine threat becomes more pressing. Green's suggestion offers a proactive approach, one that could save millions of lives if the worst-case scenario ever materializes.
