In the 1960’s, with the U.S. and the Soviet Union racing to be the first to land on the moon, the countries of the world came together to create a unified approach to ownership of celestial objects. In the 1967 Outer Space Treaty, the world’s governments agreed that no celestial body could be subject to ownership or appropriation by any nation.

The U.S. is a signatory to the treaty, but that didn’t stop the U.S. Senate from adopting the 2015 Space Act, according to The Guardian. The Act would grant exclusive rights to U.S. citizens, including private companies, who travel to space to take “space resources” that they can exploit for commercial gain.

Some lawmakers say that the Act does not contradict the treaty, since it grants rights only to individuals, and does not claim any national rights for the U.S. government. They also note that the Act allows citizens to claim rights to space resources only if they obey all U.S. laws, including all “international obligations” under the law.

But other experts in space law are troubled by the Senate Act, noting that it seems to suggest to private actors that the U.S. government will defend their rights, but denies that the government has any ownership interest. They point out that governments cannot typically grant rights to territories they do not own or control.

There has been uncertainty about the rights people would have from mining for minerals or other resources that may be found on asteroids or other planets. While some space exploration companies have offered commercial flights, such as Elon Musk’s SpaceX and Richard Branson’s Virgin Galactic, the uncertainties around mineral and other extraction rights has slowed commercialization of space mining.

But with the Senate bill, some companies are renewing their interest in space resources. The company Planetary Resources, co-founded by filmmaker James Cameron and Google’s founders, lauded the Senate vote, claiming it enshrines U.S. citizens’ rights to own asteroid resources.