What columns unqiuely identify each row of the generic lookup table?

Per the implementation in the article I can add the row (16, 'CA', 'CALIFORNIA', 'Postal.State') even though the row (16, 'CA', 'CALIFORNIA', 'Customer.State') already exists.  I'm now storing the same information multiple times in the same database - in the same table even.  Talk about your potential for "data drift."

Additionally I can add (28, NULL, 'CALIFORNIA', 'Office.State') to the same table.  I can also add 1,000 other rows for "CALIFORNIA".