While studying real estate I stumbled across the difference between business ethics, and ethics in the real world. They're not necessarily the same.
Many industries, like real estate, have created a code of ethics for their members; a firm set of rules by which they must abide. And, as long as the follow those rules, they are officially ethical.
Thing is, two 6-year-olds on the playground know the difference between right and wrong, between fair and cheating. If your industry has a code of ethics, its purpose is not to provide loopholes, to let you get away with sleazy behaviour because it's not officially sanctioned by the code of ethics.
Don't ever misbehave just because there's not a rule saying it's wrong. Ask your 6-year-old. Or mine. They'll tell you what's fair.