We should take space law seriously :  Space belongs to all humanity?  OK, fine - make that literal: create a non-governmental foundation that acts as the trustee over space for all humanity.  It would track ownership claims in space and charge periodic registration fees for that service.  And it should be the issuer of a currency that is backed by all the potential and realized value of the solar system, and accept registration fee payments only in that currency.  Its goal should be to insure that space becomes habitable and useful for all of humanity.