Dear Martin,
Thank you for your question.
According to the Guide to WIGOS [WMO-No. 1165, 2.4.1], "Any new observing facility will be given an identifier within the range allocated to the Member operating the observing facility (station/platform)". However, it is recommended, e.g. [WMO-No. 1165, 9.1.4] to "obtain WSIs for their (GCW candidate) stations from the OSCAR/Surface national focal point of the Member on the territory of which the station is operated". It is not recommended to issue a WSI for a station that is not located in the country/territory of the NFP without consulting with the country where the station is/will be located.
Currently, OSCAR/Surface is configured so that the NFP-OSCAR/Surface from a certain WMO Member can only issue WSIs with the ISO country code from his/her country as Issuer of Identifier. On the other hand, some entities and programmes have received delegated authority to issue WSIs using "specific issuer of identifier values for issuing WIGOS identifiers for observing stations that contribute to the relevant network on behalf of Members under circumstances specified in the Manual on the WIGOS" [WMO-No. 1160].
Kind regards,
Luis