Impartial, external to the projects arbitration body.
FOSS projects are often developed by international groups of people dispersed in a few countries, organised with a structure but with no formal body to keep them accountable to the law of any of the country, and even if there is a Code of Conduct in the project and someone willing to investigate and enforce it, the person is doing it in their free time. Often those who are meant to provide protection by ensuring a CoC are implicitly dependent or are part of the power structure (there is nothing like a division of powers as in modern democracies), so they actually face a conflict of interests (the reputation of the project and loyalty to those in power being on one of the sides and a fair resolution on the other, which sometimes is the opposite one) and individuals who seek protection or just a fair treatment are left by themselves.
Mobbing and is regulated by Labour Law. In FOSS with no formal employment there is no protection from mobbing.
Sexual harassment is (?) also regulated by Labor Law (?). In a regular workplace, there are legal obligations related to prevention and response, that were established to create a safe and respectful work environment. What about volunteering?
No common law, every country has its own rules. What are the legal obligations for online communities?
Project misappropriation - one person was told, by the umbrella Ombudsman, it was a mistake to make the other person a FOSS project co-admin (a common practice in anarchost, equal-power emphasising groups), they moved the reposotory (with all references, the history, GH stars and followers) because they could.