A more thorough explanation:

The Code of Professional Responsibility is a set of rules that lawyers must follow to ensure ethical conduct. It was created by the American Bar Association in 1969 and was replaced by the Model Rules of Professional Conduct in 1983.

The Code was made up of three parts: Canons, Ethical Considerations, and Disciplinary Rules. The first two parts were considered "aspirational," meaning they were guidelines for lawyers to follow, while the third part was mandatory.

The Code provided guidance on issues such as conflicts of interest, client confidentiality, competent representation, conduct to the courts, and prevention of the unauthorized practice of law. It was based on the ABA's 1908 Canons of Professional Ethics, which were borrowed from the 1887 Canons of the Alabama State Bar.

For example, a lawyer must keep their client's information confidential. This means they cannot share any information about their client's case with anyone else without their client's permission. If a lawyer violates this rule, they could face disciplinary action.

The Model Rules of Professional Conduct replaced the Code of Professional Responsibility in 1983. The Model Rules are not inherently binding but come into effect only when states choose to adopt certain rules. For example, New York state was one of the last states to continue to use the 1969 Code, only adopting a modified version of the Model Rules in 2009.