unannex
/ˌʌnˈænks/Definitions
1. verb
to remove or withdraw something from being annexed or attached to something else, especially a territory or a country.
“The unannexing of the territory led to a significant change in global politics.”
2. verb
to cancel or annul a previously made annexation or attachment.
“The government unannexed the area, returning it to its original status.”