And once again, missing some very important facts.
First of all, this involves a Marine. And Marine and Navy Retirement works differently than that of the Army and Air Force. For the first 10 years, they are actually in the "Fleet Marine (or Navy) Reserve". That is actually a non-active Reserve status, akin for the time between the end of an active enlistment and the completion of 8 years of service. And they can be recalled from this status very easily.
And secondly, he also was charged with molesting his daughter and step-daughter, starting in 2011. That is a time he was still in an active reserve status.
Charge I, Specifications 1 and 2, alleging separate instances of indecent conduct committed by the appellant against his daughter and stepdaughter between on or about January 2011 and on or about January 2012.
So if you actually looked into this case, you would see that it falls exactly as I stated. The individual was on active duty at the time of some of the offenses, therefore was recalled for prosecution. Yes he did more after he retired that were added on, but the molestation of his daughter and step-daughter was while he was still serving. Some things were added he did do later, but the original offenses unquestionably was while he was in uniform.
I find it funny that most of the articles about this case gloss over the fact that he was a serial predator, and had been one for years. For some reason they all mention his offenses after retirement, but never mention his offenses while still in. Plus he was working as a contractor on Okinawa when the child porn charges came to light. And while I am not sure what the SOFA is exactly for a civilian contractor in Japan, he should be glad he was given a Court Martial, rather than tried and convicted in a Japanese court.
And even as a civilian, there are cases where civilians actually do have to stand for Court Martial. Most specifically when under martial law. And in this case, I would say that would actually apply, as I am not aware of any US Civilian Court system in Okinawa.