Currently a table or partition can be marked no_drop or offline. This prevents users from dropping or reading (and dropping) the table or partition. This was built in 0.7 before SQL standard authorization was an option.
This is an expensive feature as when a table is dropped every partition must be fetched and checked to make sure it can be dropped.
This feature is also redundant now that real authorization is available in Hive.
This feature should be removed.