Model Rule of Professional Conduct 1.9
Definition
Rule that governs a lawyer’s duties to former clients. The rule prohibits a lawyer who represented a client in a matter from thereafter representing another party in the same or a substantially related matter in which that party’s interests are materially adverse to the interests of the former client unless the former client gives informed consent in writing. Absent the former client’s informed written consent, a lawyer is also prohibited from representing a person in the same or a substantially related matter in which a firm with which the lawyer formerly was associated had previously represented a client (1) whose interests are materially adverse to that person, and (2) about whom the lawyer had acquired material confidential information.