Research on legal ethics requires some different tools than other areas of law. We cannot rely on the standard primary sources - constitutions, statutes and codes, administrative regulations, and judicial opinions.
The only true primary sources for mandatory authority are (1) the state codes of attorney ethics (or professional responsibility) for the jurisdiction, and (2) case law. Other sources discussed herein are secondary, persuasive authority.
Secondary authority for legal ethics includes model codes, ethics opinions, treatises, books, and restatements, journal articles and current awareness sources, and foreign, comparative and international law sources.
For additional information about sources for research on legal ethics, you can consultResources for Research in Legal Ethics by Todd W. Grant (Law Annex KF306 .G73 1992). For information about legal ethics resources in Massachusetts, see section 5.6 in Handbook of Legal Research in Massachusetts, Mary Anne Neary, ed. (Law Ref KFM 2475 H36 2002).