The first piece of evidence that must be established is acceptance of the office.
Everything else follows from that.
Authority is not assumed—it must be lawfully vested. If a person claims to act under the authority of a public office, the first question is simple:
Where is the evidence that the office was accepted?
If there is no lawful acceptance of the office, then the claimed authority has not been established. Before discussing jurisdiction, statutes, policies, or procedures, the foundation of authority should be proven by the record.
Evidence first. Authority second. Everything else depends on it.