As long as the depositing insurer is solvent and the deposited securities are sufficient under this article, it may collect the income on the deposited securities. From time to time it may withdraw such securities if it deposits other securities, of the character and value specified in this article in the stead of those to be withdrawn, but deposited securities shall not be withdrawn from the State Treasury except upon the written order of the depositing insurer, indorsed by the commissioner or, if such indorsement is refused, under the authority of some court of competent jurisdiction.