CA Pub Util Code Section 150207

The authority may reduce the tax rate to a percentage lower than that approved by the voters and may further provide for an increase of the tax rate if it has previously been lowered. However, the tax rate may not be increased to a rate above the tax rate approved by the voters. Any revised tax rate may be adopted only if the authority determines, by a four-fifths vote of its members, that the proceeds of the taxes with the altered tax rate will be sufficient to provide for the payment of the principal of, and interest on, any limited tax bonds and any other indebtedness incurred by the authority which was to be payable from the proceeds of the retail transactions and use tax.