CA Rev & Tax Code Section 134

“Unsecured property” is property:

(a)

The taxes on which are not a lien on real property sufficient, in the opinion of the assessor, to secure payment of the taxes.

(b)

The taxes on which were secured by real property on the lien date and which property was later acquired by the United States, the state, or by any county, city, school district or other public entity and the taxes required to be transferred to the unsecured roll pursuant to Article 5 (commencing with Section 5081) of Chapter 4 of Part 9.