أنجليزي term (edited): Military Commission Trial Judiciary (MCTJ)

"Military Commission Trial Judiciary (MCTJ)" is a single phrase, but let us break it down.

The "Military Commission" is called المفوضية العسكرية

You may have been using a different translation for it. If so, it is time you switched.

"Judiciary" is the term we normally use for that branch of government that consists of courts, judges, magistrates, justices, etc., and handles litigious disputes. In normal contexts, we call it السلطة القضائية

The Military Commission, however, is not exactly part of the regularly constituted judicial branch of government because it is run by the Department of Defense (part of the executive branch), but it is authorized by Congress and it does conduct trials, so it has a judicial function. In order to distinguish the term "judiciary" in this context from its regular usage, I am suggesting using الهيئة القضائية

Therefore, I would translate "Military Commission Trial Judiciary (MCTJ)"
الهيئة القضائية لمحاكمات المفوضية العسكرية

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Note added at 11 hrs (2007-10-04 16:52:16 GMT)
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There is absolutely no approved "official" translation for this or related terms, and there will never be. I was one of those who advocated الهيئة القضائية in the beginning. I had to abandon that translation after a while, because I needed it for other terms. Your phrase is a perfect example of how the term الهيشة القضائية comes in handy if you have not already wasted it.