This column, written by Mark Hinderks, of Stinson LLP, focuses on ethics questions. The discussion here is based on the ABA Model Rules of Professional Conduct, but the Model Rules are often adopted in different and amended versions, and interpreted in different ways in various places. Always check the rules and authorities applicable in your relevant jurisdiction—the result may be completely different.

Question: My firm has represented a wealthy family in estate planning matters for many years. In addition, for at least 15 years, the firm represented a corporate business owned by family members in various general business matters, for which time has been billed to a general file in the company’s name. The business has been in decline, and there is no current matter. Time was last billed to the company’s general file and paid about a year ago, but the general file has never been closed. Can the firm now undertake an action adverse to the company if the substance of the action has nothing to do with and is not substantially related to any prior representation?