Also, while laws ideally are inspired by an ethical social contract, the codification proces is long, complex and far from perfect. And then for rules concerning permissible behavior even in the best of cases, it's enforced extremely sparingly simply because it's not possible nor desirable to detect and deal with all infractions. Nor is it applied blindly and equally. As actually applied, a law is definitely not even close to some ethical ideal; sometimes it's outright opposed to it, even.

Law and ethics are barely related, in practice.

For example in the vehicle emissions context, it's worth noting that even well before VW was caught the actions of likely all carmakers affected by the regulations (not necessarily to the same extent) were clearly unethical. The rules had been subject to intense clearly unethical lobbying for years, and so even the legal lab results bore little resemblance to practical on-the-road results though systematic (yet legal) abuse. I wouldn't be surprised to learn that even what was measured intentionally diverged from what is harmfully in a profitable way. It's a good thing VW was made an example of - but clearly it's not like that resolved the general problem of harmful vehicle emissions. Optimistically, it might have signaled to the rest of the industry and VW in particular to stretch the rules less in the future.