N.D. Cent. Code § 26.1-32-10

If an insurance policy requires the certificate or testimony of a person other than the insured for a preliminary proof of loss, it is sufficient for the insured to use reasonable diligence to procure the evidence and, in case of the refusal of the person to provide evidence, to furnish reasonable evidence to the insurer that refusal was not induced by any just grounds of disbelief of the facts necessary to be certified.