Thoughts from Pejman in response to a snippy post from Mark Kleiman.

Most of the discussion sidesteps the real issue, which is who is being defended, not by whom (if anyone) are we being attacked? The latter issue would only determine which government agency would be responsible for the response, not whether or not a federal response was constitutional. For instance, if the Klingons were using a gravity tractor to divert the asteroid to hit the country, then it would be up to the Air Force (or preferably the US Space Guard, if it exists at the time) to deal with it. If on the other hand, it’s a natural occurrence, then at least in terrestrial terms, it would be up the space equivalent of the Army Corps of Engineers, because it would be more in the nature of something like anticipatory flood control. Though (again preferably) both of these functions — defense and management of nature — might be under the aegis of the Space Guard. The key difference between them is that in the one case, the best defense might be a robust offense (i.e., send warships off to punish and prevent the Klingons), whereas this wouldn’t apply to a natural event.

As to whether or not asteroid defense in general, whether natural, or launched by Klingons, is constitutional, would depend to a degree on the nature of the warning we have. If, for instance, we know that it will hit the planet, but don’t know exactly where or when (and the when determines the where to a large degree, because it depends on what part of the planet has turned to be the front of it from the asteroid’s perspective at the time it hits), then it’s not just a national defense issue, but a planetary one, and we’d have to coordinate with other nations. The only acceptable solution, of course, would be to divert it from hitting the planet entirely, but in doing so, it could be that we end up making things worse (e.g., having it hit Lucifer’s Hammer style in the Pacific with accompanying ocean boiling and tsunamis, as opposed to just hitting land and creating a little ice age from all the stuff tossed up into the atmosphere, not to mention killing all the people in the vicinity).

Once we undertake to try to prevent such a tragedy, we implicitly accept legal responsibility for the outcome of our actions. I can easily imagine things getting bogged down in an international debate over the issue, which is why Rusty Schweikart wants to get the UN involved, which I can also easily imagine would only make things worse.

It’s actually similar to the arguments about hurricane diversion. Suppose we could not prevent or dampen hurricanes, but we could steer them? We might then divert them from hitting the expensive real estate in Florida but instead steer them into the Gulf where they could hit the much cheaper beaches in Mexico, for which we’d presumably compensate them. But getting these kinds of agreements would be problematic, unless (and probably even if) the level of technology was highly certain. Suppose we did have the capability to precisely steer an asteroid (this would be useful for mining them). What kind of international agreements would have to be put in place to allow us to do this? Certainly the 1972 Liability Convention would be viewed as insufficient to set hearts at ease in much of the rest of the world — no one is going to be happy about being compensated after their country has been accidentally turned into a smoking crater. I can’t see, though, how there would be anything unconstitutional per se about our doing such things.

As commenters over there note, this whole discussion mainly an opportunity for Kleiman to trot out a straw man (“Tea Partiers think that anything they dislike is unconstitutional”).