Complex sentence: The Global War on Terrorism Expeditionary Medal is a one time only decoration, however service stars may be authorized by component commanders for those who participated in extremely dangerous combat operations while performing service which entitled the GWOT Expeditionary Medal.
Split into simpler sentences: The Global War on Terrorism Expeditionary Medal is a one time only decoration. Service stars may be authorized by component commanders for those who participated in extremely dangerous combat operations while performing service entitling them to the GWOT Expeditionary Medal.