Wyo. Stat. Ann. § 9-4-903

The governor and state treasurer may sell refunding bonds at a price not less than the par value thereof and shall apply the proceeds thereof solely to the payment of a like amount of the bonds to be refunded or refunding bonds may be exchanged for a like amount of outstanding bonds. Refunding bonds may be sold or exchanged all at one time, or singly, or in blocks from time to time as determined by the governor and state treasurer, but they shall not be issued unless and until a like amount of outstanding bonds can be paid, redeemed and cancelled.