The LAW is simple: You spend the money/effort to explore new lands, it is yours. This has been the law since the very first human left his/her cave and walked to "new lands". What right do Terran governments have to impose law on extra Terran resources? Those that chose to venture into outer space will formulate their own laws that satisfy the requirements of the circumstances. Terran Law can only apply limits to affecting life on Earth.
Some people claim that we don't have the right as a species to explore/develop outer space. Well, guess what! The Earth is a part of our universe the same way a given acre or mineral resource, on Earth, is a part of Earth. What difference does it make that it is not within our atmosphere? If we can buy/appropriate land and resources on Earth than we can do the same to any part of this universe we are able to get to.