Yes, a military member can be prosecuted by court-martial for conspiracy when the object of the agreement is an offense that also exists in civilian law, but the analysis is more layered than it first appears. Article 81 of the Uniform Code of Military Justice criminalizes conspiracy, yet the object of the conspiracy must be an offense under the code. So the real question is whether the underlying civilian crime can be charged in a military court at all, and through which article. When it can, an agreement to commit it, joined by an overt act, supports an Article 81 conspiracy charge.
What Article 81 requires
Article 81 has two core elements. First, the accused entered into an agreement with one or more persons to commit an offense under the code. Second, while the agreement existed and while the accused remained a party to it, the accused or at least one co-conspirator performed an overt act for the purpose of bringing about the object of the conspiracy. The overt act need not itself be unlawful, and it must occur during or after the agreement, not before it. The conspiracy is a separate offense from the crime that is its object, and a member may be convicted of conspiracy even if the planned offense is never carried out.
The object must be an offense under the code
The phrase offense under the code is the key. Article 81 does not reach an agreement to do something that no UCMJ article prohibits. So before a member can be prosecuted for conspiracy to commit a civilian offense, the prosecution must identify the military article that makes the underlying conduct punishable in a court-martial. There are several routes.
Many acts that civilians would recognize as crimes are also enumerated offenses in the UCMJ. Larceny, fraud, assault, drug offenses, and many others appear as their own punitive articles. An agreement to commit one of these is plainly an agreement to commit an offense under the code, and Article 81 applies directly.
Reaching civilian offenses through Article 134
For conduct that is not separately enumerated, Article 134, the general article, supplies additional paths. Clause 1 reaches disorders and neglects to the prejudice of good order and discipline. Clause 2 reaches conduct of a nature to bring discredit upon the armed forces. Clause 3 incorporates noncapital federal crimes, including state offenses made federal through the Federal Assimilative …