Well, AFAIK it weren't the VW people who build the cheating system and the ones who built it, pointed out that in some countries it might be illegal to use it. The VW people just decided (probably a manager) to activate the cheat system.

So I am wondering where an ethical standard could help in that chain. If you build international products its kinda hard to know every law on this planet and refusing to build something, just because someone could use it in a country where it is illegal to use it, could become very complicated very quickly.

I think the simplest solution would be to improve the test methodologies and maybe increase the penalties.