Does Wall Street Need an Ethics Code?

Today's Wall Street Journal raised this question (subscription required). I think it is a good idea but I wonder what actual difference it will make. I mean, do we really need an ethics code to tell an investment banker that it is wrong to profit on confidential client information? Would an ethics code have prevented the 90's scandals?

So far, supporters of some kind of code are: Citigroup, Credit Suisse Group's Credit Suisse First Boston, Goldman Sachs Group, J.P. Morgan Chase, Lehman Brothers Holdings, Merrill Lynch and Morgan Stanley. I'm sure more companies will feel the pressure and join this group. Let's just hope that whatever they come up with will make a difference. I'm skeptical.