What criteria are applied in deciding which IDs should be locked?

As an example, I notice that the ID for Brigham Young is "read only" yet the one for Jesus Christ (actually headed "Christ Jesus son of Elohim") is not.

There have been a number of recent queries from members as to why IDs for their relatives are read-only, so I believe it would be of interest to know exactly what criteria are applied in determining this designation.