Exploiting the moon's resources is covered by "The Moon Treaty". Is there something similar or in the works for regulating mining asteroids and other non-lunar bodies?
The United States (along with Russia, China, Japan, India, and most other space-faring nations) did not sign (or in some cases, ratify) the Moon Treaty, and so companies that are registered in any of these countries are also not bound by it. So, that treaty is essentially pointless for anyone who actually has the ability to get to the moon in the first place.
The more relevant treaty is the Outer Space Treaty of 1967. This treaty covers a few different things; much of it is focused on prohibiting putting nuclear weapons in space, or using the Moon or other celestial bodies as military bases, etc). Article II of the Outer Space Treaty also states that "Outer space, including the moon and other celestial bodies, is not subject to national appropriation by claim of sovereignty, by means of use or occupation, or by any other means."
Basically, we can't go to a "celestial body" (more on that in a minute) and claim it as a part of the United States, say. On the other hand, Article I says, "Outer space, including the moon and other celestial bodies, shall be free for exploration and use by all States without discrimination of any kind, on a basis of equality and in accordance with international law, and there shall be free access to all areas of celestial bodies." (my emphasis added).
So Article I seems to say that anybody can go "use" the Moon and other celestial bodies, but that (per Article II), we can't claim sovereignty, or use force (or presumably coercion) to keep other nations away from a celestial body. That seems to leave open the possibility of mining an asteroid, since that's "use", as long as you don't "claim" the entire thing as a sovereign part of your country, or use force to keep other nations away.
However - and this is key - all of that hinges on what, exactly, is a "celestial body". At what point is something sufficiently large that it counts as a celestial body? The Moon, other planets in the solar system, and dwarf planets like Pluto and Ceres certainly count, but what about a medium size asteroid? What about a small one? What about a little chunk of rock, 6 inches across? Nobody has yet delineated what, exactly, is covered by the Outer Space Treaty, but it's very easy to imagine a court in the U.S. ruling that small asteroids either aren't covered, or if they are, that mining constitutes allowed "use".
And the facts on the ground (pun intended!) are that so few nations or companies have the means to get a spacecraft to an asteroid at all, that when someone does manage to do so, there won't be any practical way to contest their use of it. Treaties that the U.S. signs become law in the U.S., meaning that their interpretation can end up being decided by U.S. courts (at least, as the law applies to U.S. companies).
TLDR: legally it's a slightly gray area, but commercial mining of asteroids is probably allowed, because the treaty allows "use" of celestial bodies, and because asteroids might not even count as "celestial bodies".
I know this is an old question, but since it was asked a few things have happened, so it might be of interest to some to read an answer with up-to-date information.
There are basically two main camps when it comes to asteroid mining (I won't touch Lunar mining as that's a different can of worms):
- It's Legal: The Outer Space Treaty of 1967 does not mention asteroid mining, and thus doesn't prohibit it, so that means it's legal. Some language to that effect can be found in this well-written article published just this week.
- It's Illegal: Article II of the OST states the following: Outer space, including the Moon and other celestial bodies, is not subject to national appropriation by claim of sovereignty, by means of use or occupation, or by any other means. And as UK barrister Adam Manning explains: Private individuals, companies and so forth derive their legal rights to own land or territory through that state’s legal system. If the nation state cannot own land, it cannot grant its citizens or other legal persons the ability to do so. This would imply it's illegal.
In 2015 the US enacted a law allowing US companies to own whatever materials they removed from an asteroid (and thus profit commercially from them), and in 2017 Luxembourg followed suit with a similar law. It's rumoured that other countries are working on their own versions of this law (most notably, the UAE and China).
I'm not a lawyer, but since my business's success relies on asteroid mining being legal, I follow these matters closely. My opinion is that one of two things need to happen: 1) Enough countries pass their own asteroid mining rights laws that they all come together and agree, through some international agreement (possibly a UN treaty), that it's OK and an allowable/legal activity, or 2) A company goes ahead and mines an asteroid, and then there's an international scramble to cope with it after the fact. From a business perspective, option 1 would be the desired outcome.
In an effort to ensure it is option 1 that prevails, an international group has been formed, made up of lawyers, government officials and business people: The Hague International Space Resources Governance Working Group (full disclosure: I'm an Observer at this group). In late 2017 they released a document with recommendations of what a Space Resources treaty or set of laws should address; it's worth reading if you're interested in the matter: Draft building blocks for the development of an international framework on space resource activities.
So the short answer is that, while things have progressed in the last 4 years, the legality of asteroid mining is still in question.