Or rather, Trump has insisted that American law will recognise the possibility of private property on the Moon. And of course right behind such is going to be landlords and rentierism. This is, by the way, a good thing.
The problem is that Space Law was first codified back in those hippie dippie days of the late 1960s. Before everyone had worked through the implications of Garrett Hardin’s Tragedy of the Commons essay, Before Elinor Ostrom had even started delineating how voluntary cooperation can work – and the limits to it – and while fully one third of humanity were being impoverished by the idea that everything belonged to all.
Thus space law says that everything up out there belongs to everyone. And that’s not a system that works:
One of the things we’ve learned down here on this mortal coil about minerals is that someone has to own them. Ownership, in its most basic sense, is being able to stop someone else from taking something — the point being that it takes a lot of money (really, a lot) to go and find a nice stash of something useful. Then more money again to delineate it, work out how to raise it, process it, and get it to market. However, once all of this has been done then, it is necessary to have exclusive rights to exploit that deposit. For if anyone can just come along and dig up what has been discovered at such expense, then why would anyone spend the money to work it all out in the first place?
It has to be possible to own those mineral deposits up there. If not those mineral deposits up there never will be exploited. Thus the declaration that those deposits can be owned is a step in the right direction to their being used.