Currently there is no referential integrity between a defined Site Column and the source list that it is based on. When a list is deleted there is no warning about the impact to related Site Columns that have been defined nor the implementations of those site columns in other lists. When a list that is the source of a site column is deleted, the site column definition and all of its implementations lose their reference to the source. When trying to edit a site column for a deleted list, SharePoint gives the following error message: "List does not exist. The page you selected contains a list that does not exist. It may have been deleted by another user. Correlation ID:e6da9d9e-d00c-7000-5e4e-7715da7e2d53"