Law is an expression of public policy decisions. Sometimes the public policy intentionally permits less than laudable conduct. The employment-at-will doctrine comes to mind as an example. To encourage employment, the law gives free reign to employers to dismiss employees - even if the grounds for the dismissal seem unfair. See posts: Fired For Racial Tolerance; Fired For Choice of Necktie; Fired For Wearing Orange Shirts.
Ethics, on the other hand, carry no such hidden agenda. Ethical principles encourage doing the right thing, independent of considerations of expediency, efficiency, profit or other purportedly justifiable circumstance. In short, ethics is about the "Broterhood of Man." As in:
There is a Brotherhood of Man,
A Benevolent Brotherhood of Man,
A noble tie that binds
All human hearts and minds
Into one Brotherhood of Man.
Your lifelong membership is free.
Keep agivin' each brother all you can.
Oh aren't you proud to be
In that fraternity,
The great big Brotherhood of Man?
Oh, that noble feeling,
Feels like bells are pealing,
Down with double-dealing,
You, you got me;
Me, I got you, you!
From "How to Succeed in Business Without Really Trying":
Matthew Broderick - click on image below: