Dropdowns/Select with changing list of items

I have "dropdowns" and "select inputs" that are fed from a remote endpoint. The list of items coming from the endpoint changes over time, so it's possible that an option selected some time ago is no longer available as of a more recent date.

I still need to let users go back in time and edit a former element. But I am unsure how to handle the fact that and old item selection made sense back in that time, but not anymore.

What is the best user experience when a user edits an old document with a no longer valid option in a dropdown/selector?

  1. Preserve the outdated selection just to keep the story consistent.
  2. Force the user to pick a new element from the currently valid selections.