Restitution and Antipropertarians
Anarchists usually fall into one of two categories, pro-property, or anti-property. Pro-property usually means "coming from a Libertarian angle", anti-property usually means "coming from a socialist angle". I'm gonna call them "propertarian" (from the word "property") and "antipropertarian".
Antipropertarians usually substitute possession-and-use for what the propertarian calls "property". They're similar concepts, but not the same. But I think I've found that, in the context of restitutive justice, they're actually compatible.
To illustrate this, let's suppose we have a propertarian farmer and an antipropertarian farmer. The propertarian farmer sees the others' land and thinks "that's his property", whereas the antipropertarian farmer looks at the other's land and thinks "he is using it and it is in his possession". The antipropertarian notices that the propertarian has left a field fallow for 10 years. They're not using it, and probably won't be using it anytime soon. In the eyes of the antipropertarian, the other farmer is no longer using it, making it free for him to put to use himself. Assuming they can't or don't agree on how to use the land, the antipropertarian may do what he sees as his right - he starts cultivating the empty field and grows and harvests a crop. The propertarian farmer may be none to happy about this. What does he do?
According to Rothbardian and Lockean property theory, the antipropertarian did the work, which created the property right in the crop. And, according to the principles of restitutive justice, there has been no damage done to the land itself that would allow for cause of action against the tresspasser. The propertarian should have the right to force the antipropertarian to repair all damage done, but what damage is there for the antipropertarian to fix? There was no cost to the propertarian at all. If the propertarian claimed the crop which the other farmer harvested, he would be stealing.
Ultimately, there is no action that can be rightly taken against the antipropertarian.
This doesn't just apply in this one case. A propertarian not living in a house they own may find it has been moved into by an antipropertarian. Hold the antipropertarian responsible for any damage done to the property, but cause of action does not extend beyond that, no cause of action exists for the "crime" of living in a house so long as it has been maintained. An irresponsible squatter would certainly be held liable for any damage done to the property, a responsible squatter would not have done any damage to be held liable for.
In every case I've been able to think of where a propertarian and an antipropertarian disagree about whether a crime has been committed, the crime is of such a nature that no restitution can rightly be demanded, rendering it effectively no crime at all for all practical purposes.
This does of course depend on restitutive justice. A system of retributive justice can't guarantee the same level of interoperability between the two that restitutive justice does. I see this as just more reinforcement for my position of strictly restitutive justice, but take whatever conclusions you want from it.