This guide is an introduction to researching legal ethics and professional responsibility in the United States, with a special focus on Texas. It covers free online resources, subscription databases, and the major books and periodicals available in the Dee J. Kelly Law Library. This guide is intended for use by Texas A&M University School of Law students and some of the resources listed may only be available to current students. Those resources will be marked by a key symbol ().
As members of the legal profession and officers of the court, lawyers are required to follow rules of professional conduct that are mandated either by a state legislature or by the highest court in the state. These rules govern both the public and the private behavior of lawyers. Because they are licensed to practice by the states, lawyers who violate rules of professional conduct are likewise disciplined by the states, not the federal government. The punishment for violating a state rule of professional responsibility ranges from private or public reprimand to suspension or disbarment (permanent disqualification from practicing law in the state). To the limited extent that they practice law, judges are also subject to the state code of professional conduct in addition to a Code of Judicial Conduct. 
Researching issues in professional responsibility is a complex process and requires use of materials beyond basic court opinions and statutes. At the core of issues of legal ethics are the state rules governing the conduct of lawyers and judges. These state rules are based on model rules adopted by the American Bar Association, most recently the Model Rules of Professional Conduct and the Code of Judicial Conduct. Although these model rules are not binding, they are the foundation for the vast majority of state professional conduct rules. This makes the ABA model rules and their annotations highly influential when it comes to interpreting state rules.
In addition, each state's bar association has some mechanism for enforcing the rules through disciplinary proceedings and through the issuance of opinion letters or ethics opinions on ethical issues submitted to the bar or its ethics committee. Opinion letters and ethics opinions are not binding, but are highly influential in their jurisdictions.
Therefore, to properly research the conduct rules of your state, you will need to consult the following at a minimum:
After researching these materials, you may find that you need to do further research in the case law. This can be challenging, because ethics issues can arise both from attorney discipline proceedings and from such substantive areas as legal malpractice and criminal appeals. Since most legal practitioners have some experience finding case law, this guide will focus on the other materials, although a few tips on finding judicial decisions in the area of legal ethics are included.
 Summary adapted from Professional Responsibility, TheFreeDictionary.com, http://legal-dictionary.thefreedictionary.com/Professional+Responsibility (last visited Dec. 18, 2017).
These guides from other universities may help you find additional research sources. Please note that these guides are written for students attending those universities, so some of the resources they list may not be available to students from other institutions.