Right, you can live in the jungle and not have any contracts, or you can choose to live in a community and set up explicit rules among property owners, or on your own property. AnCaps can very well enforce contracts. This contract can prohibit the eviction of Children, unless they can be transferred safely to another Guardian.

Someone can offer to pay to become the new Guardian, but they are still bound by the same inherent condition of Guardianship - if they abuse the Child, they will owe compensation and may have their position contested in a manner similar to contesting the abuse of an unconscious individual.

The outsider can operate on the base assumption that the victim would want protection from aggression, and engage on their behalf until they regain control.