In 2015, the U.S. Congress passed H.R. 2262, the U.S. Commercial Space Launch Competitiveness Act. In addition to legalizing space exploration by private companies, it states, "A U.S. citizen engaged in commercial recovery of an asteroid resource or a space resource shall be entitled to any asteroid resource or space resource obtained." That is, anything an American citizen finds in space, she can keep, use, and sell as she sees fit.

In 2016, the country of Luxembourg followed suit with a similar law. While it might seem strange for the tiny country to be the second in the world to pass such a law, it does make sense: in the months previous, the government announced a new commercial space initiative and invested $28.5 million in the asteroid-mining company Planetary Resources. Motherboard has called the country a global leader in asteroid mining.

But is making commercial mining legal actually, well, legal? There is one international law that could cause a problem: The Outer Space Treaty of 1967. It says that "outer space is not subject to national appropriation by claim of sovereignty, by means of use or occupation, or by any other means."

The U.S. and Luxembourg say their laws don't violate the treaty, since no sovereign nation is actually laying claim to an area of outer space; it's just private entities laying claim to individual resources. Whether or not that holds up in international court will have to wait until the first company brings back the spoils of space mining.