Army Regulations. See, e.g. AR 27-10, Military Justice; AR 27-26, Rules of Professional Conduct for Lawyers.
ABA Standards for Criminal Justice. The standards are intended to be used as a guide to professional conduct and performance. According to AR 27-10, para. 5-8c, “Judges, counsel, and court-martial clerical support personnel will comply with the American Bar Association Standards for Criminal Justice (current edition) to the extent they are not inconsistent with the UCMJ, MCM, directives, regulations . . .or other rules governing the provision of legal services in the Army.” The Standards have discussion sections that deal with many of the thorny issues counsel run into when investigating their cases.
Case Law. See, e.g. , Geders v. United States, 425 U.S. 80, 90 n.3 (1976) (“An attorney must respect the important ethical distinction between discussing testimony and seeking improperly to influence it.”).