Code of Ethics Doesn't Influence Decisions of Software Developers (csc.ncsu.edu)

Well, that's a bummer. Still, I can think of considerations with a "code of ethics" aside from direct prevention. Certainly easier to deal with a violation after the fact, if you don't have to argue about what the expectations even were.

If a policeman tickets you for speeding, there's not usually any argument over whether speeding is legal or not. "No speeding" is codified by law.