JAGs, even those in the NLSO, have sailors as clients. There is no conflict with big Navy. Even if crosswise with the Navy, as in UCMJ, a JAG appointed will represent the military member wholly and completely with no conflict. That is his ethical duty. If simply consulting with a staff JAG doing acquisition work for a syscom, or some sort of thing, well yes, he represents one party already. That is why he likely won't give specific advise on a particular deal. To do so would be unethical and for a JAG is the sort of thing that could have career implications.