Under Rule 1.9, what is prohibited after a lawyer has left a previous representation?

Under Rule 1.9 of the California Rules of Professional Conduct, a lawyer is prohibited from representing a new client with materially adverse interests to a former client in the same or a substantially related matter. This rule is in place to protect the confidentiality and loyalty owed to the former client, ensuring that no sensitive information obtained during the previous representation can be used to the disadvantage of that former client in a new case.

This obligation continues even after the representation has ended, reinforcing the importance of the trust and confidentiality inherent in the attorney-client relationship. Adverse representation can create conflicts and undermine public confidence in the legal profession, which is why this prohibition is strictly enforced. Thus, the correct choice regarding what is prohibited after leaving a previous representation is accurately represented in the choice regarding materially adverse interests in the same matter.

Other options, such as representing new clients in unrelated legal matters or discussing prior cases with new clients, do not inherently conflict with the duties owed to former clients, provided there is no risk of using confidential information against a former client. Similarly, providing legal advice to former clients generally does not violate any rules unless it pertains to a new matter where conflict arises.