SQL & PL/SQL

I just received a unique constraint violation error message when I tried to insert a row into a table.
But even after I deleted the PK constraint on the table in question, I still get the same error message when I retry the insert:
SQL Error: ORA-00001: unique constraint (GILLNET_TAG.DELETED_AUTH_PK) violated
00001. 00000 - "unique constraint (%s.%s) violated"
*Cause: An UPDATE or INSERT statement attempted to insert a duplicate key.
For Trusted Oracle configured in DBMS MAC mode, you may see
this message if a duplicate entry exists at a different level.
*Action: Either remove the unique restriction or do not insert the key.

Can somebody tell me why? Is the constraint deletion simply not registering with SQL Developer?
Thanks.