What action must a lawyer take according to Rule 1.16 if a client insists on an illegal action?

A lawyer must withdraw from representation when a client insists on engaging in illegal conduct. This obligation stems from the ethical requirements set forth in Rule 1.16 of the Model Rules of Professional Conduct, which emphasizes the responsibility of attorneys to maintain lawful practice and uphold the integrity of the legal profession.

If a client is intent on pursuing illegal actions, continuing the professional relationship may not only compromise the lawyer's ethical duties but could also expose the lawyer to potential legal and disciplinary repercussions. By withdrawing, the lawyer can ensure that they do not participate in or facilitate any illegal conduct, thus maintaining their professional integrity and compliance with the law.

Other options do not align with the lawyer's ethical obligations. For instance, going along with a client's request or choosing to ignore it fails to address the fundamental issue of legality and professionalism. Prosecuting a client regardless of legality contradicts the lawyer's duty to act in accordance with the law. Hence, the only appropriate response when faced with such a situation is to withdraw from representing the client.