Professional responsibility (also known as legal ethics) refers to the law governing lawyers' conduct.
Each state has a set of rules in the area. Almost all states have adopted the American Bar Association's Model Rules of Professional Conduct, sometimes with some variations. The official comments to the Rules of Professional Conduct help researcher's understand the rules. (California is the only state whose rules follow a different format.)
In addition, the practice of law is governed by state statutes and rules concerning the admission to practice and attorney discipline. The rules and statutes are interpreted by bar associations (in formal and informal ethics opinions and in disciplinary proceedings) and by courts.