ADVERTISEMENT ADVERTISEMENT Avoiding Materially Adverse Conflicts After New ABA Opinion Law360 (February 18, 2021, 3:32 PM EST) -- On Feb. 10, the American Bar Association's Standing Committee on Ethics and Professional Responsibility published ABA Opinion 497, which provides long-needed guidance on what constitutes "materially adverse" interests between clients.[1] Rules 1.9(a) and 1.18(c) of the ABA Model Rules of Professional Conduct prohibit a lawyer from representing a current client with interests that are materially adverse to those of a former or prospective client on the same or "substantially related matter."[2] While the prohibition is clear, neither rule — nor the accompanying comments — explains what constitutes materially adverse interests.[3]