I kind of like the idea of voluntary contracts that form the ground rules for basic "legal" behavior, but I haven't solved the problem of those who would chose no contract at all.
Manwich tried attacking the DRO idea over this concept in a show awhile back. He called them "rogues", and claimed the only reason someone would want to live like that is so they wouldn't be bound by any contracts, making it easier to engage in criminal activities. He then asked Ian, who was defending the DRO concept, what the DROs would do about that.
I sent in an e-mail that didn't make it on the air about it. My point was that if there's only a few of these "rogues", then it's a non-issue. Above a certain threshold number of rogues, DROs would include a clause in their contracts forbidding their customers from participating in commerce with rogues (though people wouldn't want to deal with rogues in the first place, as you would have no recourse if one cheated you).
Thus, rogues would only be able to deal with other rogues. But even rogues, when they're not being criminals, have to eat. This creates an undergound economy of rogues that trade with each other for the necessities of life. However, rogues don't like getting cheated any more than you or I do. So, they form their own DRO-like entities to protect their legitimate trades between each other. At some point, it will make business sense for the rogue's DRO to open itself up to the other DROs, and then the rogues aren't rogues anymore. If that ever happened in real life, which I think is pretty damn unlikely, it would be a solved problem.