The UCMJ (Uniform Code of Military Justice) is a very different beast. There are many things that are considered major offenses under the UCMJ that are not offenses in the civilian courts, and by signing on the dotted line the service member has agreed to be held to that higher standard.
If this is a new relationship I would advise the service member to step back as this could cause him problems. If this is a relationship that preexisted his entry into the military or is otherwise long term; he may consider speaking to his chain of command and seeing if there are any waiver options that may apply to his situation.
He should be aware that if his relationship with his chain of command is not a good one; he may be putting himself in a situation where he is admitting to conduct that could result in an NJP or worse. If that is the case I would advise him to contact the base JAG office or a local attorney with military/JAG experience and consult with a them as to the proper course of action.
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More information is needed to answer your question. If by dating, you really mean having sex, than the servicemember will not be charged by the military as the legal age of consent is 16 years of age. This, however, does not mean that the state of NC could not charge him if the age of consent in NC is say 17 or 18 and they are having sex off base. Feel free to give my office a call if you need additional advice. Good luck.
You are allowed to date! It is completely legal in North Carolina. If on the other hand you are talking about sex, it is still legal under those circumstances in North Carolina. You could run into trouble if she complains to your superiors. It is best to wait on anything more than dating until she turns 18.