restrict modification of column values in BR triggers - Mailing list pgsql-hackers

is there any way to prevent role from modifing values of some columns of NEW row in before row triggers? I revoked insert privilege from these columns to ensure that only default value can be inserted, but it is still posible to modify values being inserted using before row triggers. I can't revoke trigger privilege on that table, because this role must be able to create triggers on this table.