N.D. Cent. Code § 26.1-05-25

A domestic life insurance company, at any time, may change the securities on physical deposit or designated on the statement of securities held by the company in lieu of a deposit by substituting a like amount of the character required in the first instance. If the annual valuation of the policies in force shows them to be less than the amount of the security deposited, the company may withdraw the excess, but at least twenty-five thousand dollars worth of securities must remain on deposit at all times.