Thank you for your question. The Uniform Code of Military Justice does not make such conduct illegal.
However, Adultery is still a prosecutable offense under the UCMJ. The UCMJ is a federal law, enacted by Congress, to govern legal discipline and court martials
for members of the armed forces
. Articles 77 through 134 of the UCMJ encompasses the "punitive offenses" (these are crimes one can be prosecuted for). None of those articles specifically mentions adultery.
Adultery in the military is actually prosecuted under Article 134
, which is also known as the "General Article." Article 134 simply prohibits conduct which is of a nature to bring discredit upon the armed forces, or conduct which is prejudicial to good order and discipline.
The UCMJ allows the President of the United States to administer the UCMJ by writing an Executive Order, known as the Manual for Court Martial (MCM
). The MCM includes the UCMJ, and also supplements the UCMJ by establishing "Elements of Proof," (exactly what the government must *prove* to prosecute an offense), an explanation of offenses, and maximum permissible punishments for each offense (among other things). While the MCM is an Executive Order, enacted by the President, in reality much of the contents are a result of military and federal appeals court decisions.
One of the things that the MCM does is to expand article 134 into various "sub-articles." One of these "sub-articles" covers the offense of adultery (Article 134, paragraph 62).
Adultery, as a military offense, is difficult to prosecute (legally) for several reasons.
There are three "Elements of Proof" for the offense of Adultery in the Military:
(1) That the accused wrongfully had sexual intercourse with a certain person;
(2) That, at the time, the accused or the other person was married to someone else; and
(3) That, under the circumstances, the conduct of the accused was to the prejudice of good order and discipline in the armed forces or was of a nature to bring discredit upon the armed forces.
Element #2 is usually pretty easy for the government to prove. There is normally sufficient written evidence to prove whether or not someone is legally married. (Many folks will be surprised to learn that in the military, a single person can be charged with the crime of adultery).
Element #1 can be very hard to prove. Remember, a court martial (like civilian court) requires *proof* beyond a reasonable doubt. Proof of sexual intercourse normally requires photographs, a confession of one of the parties involved, an eye-witness, or other legally admissible proof. (The mere fact that someone stayed over at another individuals house, or even slept with them in the same bed is not proof of sexual intercourse.
Element #3, in many cases, can be the most difficult item to prove. The government must show that the individual's conduct had some direct negative impact on the military. This normally would include cases of fraternization
& enlisted) or a relationship with another military member, or a military spouse.
The military will rarely prosecute such cases, if at all, as an executive order has been issued to discourage such prosecutions.
So to sum up, the conduct of which you are speaking does not rise to the level of a violation of US military law