If exploitation of outer space’s bounty is our goal, we must establish a space property legal system that creates both incentives and predictability. Space development is a highly risky endeavor, as well as mind-bogglingly expensive. Who would expend the effort in developing a space colony, if they were not certain of the project’s legality? Valuable projects — energy collection, mining, and colonization — are by no means inevitable. If the law of outer space rejects such uses, or even makes their legality uncertain, it is unlikely that the nec-essary technology would ever be created. A promising solution to our ever-growing energy needs involves setting up giant banks of solar panels in Earth’s orbit and on the moon’s sunny side, using the solar energy to power space development projects, and then beaming the excess down to Earth as microwave energy for terrestrial use.2 Will a private electric company be willing to develop such a lunar solar collection system? Not without a field of space law that permits exploitation and a strong rate of return on investment. Unless we can impose a rule of law that eliminates uncertainty while permitting the highest possible rate of return, we may be denied access to the fruits of space for a long time to come.