Property rights are not fair: it is up to individuals to protect themselves in the sphere of relationships. Married couples have entered into a state-endorsed relationship which provides advantages (both financially in terms of taxes and inheritance, and through recognition and validation). It is reasonable for the state to require something in return: namely, that the parties are treated fairly, should that marriage end. Moreover, married couples are forced to share their property because they have chosen to commit themselves to each other. When people get married they know what they are signing up to and can therefore be taken to consent.