If you are a table owner, you can drop the encryption or encryption key on a column by using alter table with the decrypt option.
The syntax is:
drop encrypton key [database.[owner].]keyname
For example, to drop encryption on the creditcard column in the customer table, enter:
alter table customer modify creditcard decrypt
This drops the encryption key on a column:
drop encryption key cust.dbo.cc_key
The System Security Officer and key owners can drop keys. A key can be dropped only if there are no encrypted columns in any database that use the key. drop encryption key cannot check suspect and offline databases for columns encrypted by the key. The command issues a warning message naming the unavailable database, but does not fail. When the database is brought online, any tables with columns that were encrypted with the dropped key are not usable. To restore the key, the System Administrator must load a dump of the dropped key’s database from a time that precedes when the key was dropped.
