USS Arizona decommissioned
The Arizona was not decommissioned. Rather she was stricken from the Official Register of U.S. Navy ships on 1 December 1942. Ships that are sunk in action are not decommissioned; they are stricken from the register. Only ships on the register can be in commission.
The Naval Vessel Register itself lists her as decommissioned on 12/29/41: http://www.nvr.navy.mil/SHIPDETAILS/SHIPSDETAIL_BB_39_1820.HTML