No one has managed to pluck valuable minerals from an asteroid quite yet, but when they do, the legal framework will be firmly in place: earlier today, President Obama signed the US Commercial Space Launch Competitiveness Act (CSLCA) into law.
The bill deals with a few aspects of space travel: it extends America's commitment to the ISS into the next decade, loosens the regulatory burden on space startups, and deals with the legalities of asteroid mining.
There's now a framework for establishing property rights on a celestial body for mining purposes. Although the 'celestial body' itself can't be claimed by a country or company -- that flag on the Moon doesn't actually mean it belongs to the US -- anything mined by a company is now its to keep.
When getting to those asteroids, private spaceflight companies are now subject to less regulation. Although the likes of SpaceX and Virgin Galactic are still accountable to the FAA, regulations are looser than those placed on the rest of the aviation industry.
All in all, it's a coup for asteroid mining companies like Planetary Resources and private spaceflight companies alike -- not to mention their lobbyists, of course.