Guest Post – Planetary Defense and International Law: Balancing Risks

I’m very pleased to host a guest post from an old friend of mine, and A-list international law academic, James Green.  James is Professor of Public International Law at Reading University. He has written widely on international use of force law, WMD proliferation law, and he most recently wrote an acclaimed book on the persistent objector principle.

In this post, James considers what would happen if Bruce Willis movies predicted the future.  I’ll leave it to James to explain 🙂

But seriously, this is in fact a very interesting legal area due to the various treaty and customary law principles it implicates. Take it away, James . . .


Planetary Defense and International Law: Balancing Risks

By: Dr. James A. Green

Professor of Public International Law, University of Reading (UK)


Major asteroid impact is a low-probability, but high-consequence risk.  Large ‘Near-Earth Objects’ (NEOs) don’t hit Earth often, but there have been at least 5 extinction-events in the history of our planet because of such impacts (not least, the end of the dinosaurs). Of course, low probability risks are easily dismissed, however high the consequences of them manifesting might be, and, until recently, the countries of the world largely viewed the threat posed by NEOs as something best left to Hollywood films like Armageddon or Deep Impact.  Limited funding, a lack of coordinated strategies and infrastructure, and a pervading absence of political will all meant that – had a large collision-course asteroid appeared 20 (or even 5) years ago – our chances of responding to it in time might have been pretty slim.

But that’s all changed, following the impact (in more ways than one) of the meteoroid that hit Chelyabinsk in Russia in 2013, which injured over a thousand people. Suddenly, the NEO threat became ‘real’, and major players – the US, Russia and the EU – all started pumping money into NEO preparedness, and developing formal strategies for response (see, for example, the production of the US’s first ever National Near-Earth Object Preparedness Strategy in December 2016).  At the UN, we’ve witnessed the recent creation of an embryonic international institutional infrastructure, with new inter-state bodies to detect (IAWN) and respond (SMPAG) to asteroids.  The risk of asteroid cataclysm hasn’t changed – it’s still extremely unlikely any time soon, but very likely at some point in the next 100,000 years (who knows when?) – but what has changed is that humanity now has the global political will and infrastructure to begin to be in a position to respond, if needed.

Alongside this, there is an increasingly strong, if not unanimous, scientific view that the use of nuclear weapons would in many cases be our best hope of responding to a collision-course NEO.  NASA has quantified the use of nuclear weapons as being between 10-100 times more effective than any non-nuclear alternative.  In line with this view, the newfound (post-Chelyabinsk) governmental and inter-governmental focus on NEO preparedness has particularly engaged in developing what we might term the ‘nuclear option’.  For example, even before the end of 2013, the US and Russia had mooted working on a nuclear planetary defense initiative together.  That now seems to be on hold given current tensions between the two states (Crimea, Trump’s election, Salisbury, you name it), but the very fact that these nations – given their shared nuclear history – seriously considered the possibility of joint nuclear action against asteroids speaks volumes.

At the start of the current decade, ‘nuclear planetary defense’ was the plot of a silly Bruce Willis movie from the 90s; now it is a genuine possibility, which the nuclear powers and the UN take very seriously.

Ok, but isn’t Arms Control Law a legal blog?   What does all this mean for international law?  Fairly obviously, the notion of ‘nuclear weapons in space’ is one that sits at the intersection of arms control (and specifically nuclear non-proliferation) law and space law. Various Cold War era treaties (most notably, the Outer Space Treaty; the Limited Test-Ban Treaty) would seemingly rule out potential nuclear planetary defense scenarios.  Admittedly, depending on circumstances, that legal conclusion will not always be entirely clear – the relevant law was drafted with the superpower arms race in mind, after all, not asteroids, and not all states are parties to all the relevant treaties, etc etc – but, to over-simplify a little, as things stand nuclear strikes against asteroids would likely violate international law.

One might reasonably argue that this is as it should be.  The asteroid risk is low, and so is one worth taking; the threat posed by nuclear weapons in space is far more acute than that of some hypothetical space rock.  It’s not hard to envisage nuclear states using the vague threat of ‘asteroids’ as a pretext for developing new warheads, or even for launching nukes into space as a ‘pre-emptive’ measure of planetary security; making us all much less secure.  The threat of NEOs acts as a convenient narrative for the nuclear powers in the face of prohibitive space and non-proliferation law regimes: all the more reason, perhaps, to reaffirm those regimes.

Readers of this blog will be extremely familiar with recent developments in nuclear non-proliferation, perhaps most notably the adoption of the final text of the Treaty on the Prohibition of Nuclear Weapons (TPNW) in 2017.  They will also likely know of, although perhaps may be a little less familiar with, recent attempts to strengthen space law de-militarization and arms control provisions, and particularly the growing support for the Draft Treaty on Prevention of the Placement of Weapons in Outer Space and of the Threat or Use of Force against Outer Space Objects (PPWT, latest draft text 2014).  Neither the TPNW nor the PPWT are in force yet, of course (and may never be, at least for the nuclear powers).  But if they were, either would unequivocally rule out any and all nuclear planetary defense, and – even as things stand – they at least point to a competing trend in international politics that is in direct opposition to the notion of nuking NEOs.

However, realistically, such initiatives are not going to lead to complete nuclear disarmament any time soon, and the political developments we have seen since Chelyabinsk now mean that nuclear planetary defense is genuinely entertained at the international level, whether or not we might find that fact desirable.  At least one nuclear power has already indicated that – if the ‘killer asteroid’ appeared – it likely would ignore international law (both Cold War era and developing) entirely, opting for ‘launch first, litigate second’.  International law shouldn’t be a global suicide pact, and saving humanity is pretty compelling stuff; a rigid adherence to Cold War era treaties in the face of global annihilation would be hard to support.  Equally, ignoring the law is always a dangerous and damaging business.  Perhaps it may be better to build in a little room, now, for international law to bend, than to risk it breaking at a crucial moment.

In a major article published this week in the Hastings International & Comparative Law Review, I chart all the recent ‘asteroid preparedness’ developments in detail, and set out the case for the current illegality (in most instances) of nuclear NEO response.  I also consider a range of possible ways that such illegality could be precluded, ranging from the likes of ‘necessity’ to treaty withdrawal/suspension; some of these possibilities may be more suitable than others, but all would be problematic.   Ultimately, I argue that international law needs to strike a balance: the law has to protect us from states using asteroids as a pretext for dodging nuclear disarmament obligations, or – much worse – nuclear aggression in space, broadly keeping the long-standing Cold War era prohibitions in place.  At the same time, we should look to develop a limited, safeguarded exception – only for instances where an asteroid threat had been verified and was actual, not potential – that would allow for multilateral nuclear planetary defense, in the unlikely event that we need to resort to the ‘nuclear option’ to save ourselves.  When it comes to asteroids, since 2013 the political and scientific context has changed astronomically (if you’ll forgive my use of that word here…); we need to ensure international law is best placed to respond to those changes, if it ever has to.


One Comment on “Guest Post – Planetary Defense and International Law: Balancing Risks”

  1. Thanks for an interesting post! With regard to the question of the legality of a nuclear strike, wouldn’t the obvious solution to the “suicide pact” conundrum be to involve the UN Security Council? If they approve the mission, the treaty obligations you mention should have to yield, UN Charter article 103. And there should be little risk of a vetoed given the shared interests of states in responding.

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