Usually not as a complete defense, but the answer depends heavily on the offense charged. Military law generally treats ignorance or mistake of law as no defense, and many customs-and-courtesies violations are general intent offenses where the member’s lack of awareness does not excuse the conduct. There are, however, narrow situations where knowledge of a particular duty is itself an element the government must prove, and there the absence of training can matter. The distinction between these categories is where this question is won or lost.
The general rule: ignorance of law does not excuse
The starting point is a long-settled principle. Ignorance or mistake of law, including ignorance of general orders and regulations, is ordinarily not a defense in military justice. The classic example is that not knowing it is unlawful to possess a controlled substance is no defense to possessing it. The same logic applies to many obligations that flow from military custom. The fact that a member was never specifically taught a particular courtesy, or did not realize a custom carried disciplinary weight, generally will not excuse a violation if the conduct itself is prohibited.
This rule exists for a practical reason. If lack of training were a blanket defense, discipline would depend on each individual’s instruction history rather than on shared standards. Military service presumes that members are responsible for conforming to the established norms of the service, and those norms include customs that are not always written down in a single regulation.
General intent offenses and why training gaps rarely help
Many of the offenses tied to military customs are general intent crimes. Disrespect toward a superior, contempt toward officials, and similar conduct turn on whether the act or words were objectively disrespectful or contemptuous under the circumstances, not on whether the member subjectively understood the relevant custom. For these offenses, the government does not have to prove that the accused knew a custom existed or had been trained on it. A member who claims, “no one ever taught me that was disrespectful,” is making an argument that the law generally does not recognize as a defense to a general intent charge.
That does not make the training history irrelevant. It can still be powerful in mitigation. A genuinely inexperienced member who acted out of ignorance rather than defiance may receive a more favorable disposition, a lesser charge, or a lighter sentence. Mitigation and defense are different things, and lack of training tends to live on the mitigation side of that line.
Where knowledge of the duty is an element
The picture changes for offenses that make knowledge of a specific duty part of what the government must prove. Dereliction of duty under Article 92 is the leading example. A duty can arise from many sources, including the custom of the service, but the accused must have known of the particular duty for a dereliction conviction to stand. If a duty rests solely on a service custom that the member was never taught and could not reasonably have known, the absence of that knowledge can defeat the knowledge element.
This is a meaningful but limited opening. It applies to offenses where knowledge of the duty is a required element, and it requires more than a bare assertion. The member must show that the duty depended on a custom outside ordinary awareness and that the member genuinely lacked knowledge of it. Where the duty is obvious, widely understood, or covered by routine instruction, a training-gap claim will not hold up.
A narrow exception involving reliance on authority
There is also a recognized but narrow exception to the ignorance-of-law rule. A mistake of law may be a defense when it results from reliance on the decision or pronouncement of an authorized public official or agency responsible for administering or enforcing the law in question. This is not the same as lack of training. It applies when a member was affirmatively told by a proper authority that conduct was permissible and acted on that guidance. Notably, reliance on a private attorney’s advice does not qualify. This exception will rarely apply to ordinary customs questions, but it is worth knowing because it marks the outer boundary of when a legal misunderstanding can excuse conduct.
How to use the argument effectively
A service member raising lack of training should match the argument to the offense. For a general intent customs violation, the realistic goal is mitigation: documenting limited time in service, the absence of relevant instruction, and the lack of any defiant intent to argue for reduced charges or punishment. For a dereliction or other knowledge-based offense, the argument can attack an element directly, but it needs evidence that the duty rested on an obscure custom and that the member truly did not know of it.
Counsel can develop this through training records, the member’s experience level, witness testimony about what instruction was actually provided, and the nature of the custom at issue. Framing matters: an honest, well-supported account of inexperience is more persuasive than a claim that sounds like an excuse.
Bottom line
Lack of training on military customs is generally not a standalone defense, because ignorance of law does not excuse and most customs offenses require only general intent. It can be a complete answer in the narrow class of offenses, such as dereliction of duty, where knowledge of the specific duty is an element, and it is frequently valuable in mitigation. Because the outcome depends on the precise charge and the source of the duty, a service member in this situation should consult a qualified military defense attorney to evaluate how the argument applies to the specific allegations.
Disclaimer
This article is provided strictly for general educational and informational purposes. It is intended to explain how the Uniform Code of Military Justice (UCMJ), the Rules for Courts-Martial, the Military Rules of Evidence, and related military administrative processes work as a matter of public legal education. It does not constitute legal advice, a legal opinion, or a recommendation about any particular case, and it is not a substitute for advice from a qualified military defense attorney who can evaluate the specific facts and command, service, and jurisdictional circumstances involved.
Reading this article, or contacting any website on which it appears, does not create an attorney-client relationship between the reader and any law firm, attorney, or author. Every court-martial, nonjudicial punishment action, administrative separation, and security-clearance matter turns on its own facts, the charged articles, the convening authority, the service branch, and the evidence, and outcomes vary widely from one case to another.
Military law also changes over time. The Military Justice Act of 2016 (effective January 1, 2019) and subsequent National Defense Authorization Acts renumbered and rewrote many punitive articles, revised the Article 32 preliminary hearing, and altered sentencing, clemency, and appellate procedures. Statutes, regulations, executive orders, the Manual for Courts-Martial, and decisions of the service Courts of Criminal Appeals and the Court of Appeals for the Armed Forces may have been amended, superseded, or reinterpreted after this article was written, and article numbers or procedures cited here may have changed.
For these reasons, no reader should act or decline to act based on this content without first consulting a licensed attorney experienced in military justice about their own situation. The author and publisher make no warranty, express or implied, as to the accuracy, completeness, timeliness, or current applicability of the information provided, and disclaim any liability for any action taken or not taken in reliance on it. If you are facing investigation, charges, or an adverse administrative action, time limits may apply, and you should seek qualified counsel promptly.