Where should retired Nigerian senior officers be tried?

An interesting situation is developing in Nigeria, where several retired flag and general officers are under investigation in a major corruption case. Where should/can they be tried? Here's an article that gives one retired officer's view:

IN furtherance of its investigation into the arms purchase scandal under the immediate past administration of former President Goodluck Jonathan, the Economic and Financial Crimes Commission (EFCC) recently bared its fang on the former chief of air staff, Air Marshal Adesola Amosun. 

Amosun’s arrest added more to the list of other 17 former high-ranking officers, including chief of defence staff, Alex Badeh, who are being questioned by the anti-graft agency for alleged weapons procurement fraud. 

But in view of the reactions by some Nigerians who see the action of the EFCC as an affront against the military institution, Sunday Sun sought the opinion of a respected retired Army General and one time minister of police affairs, General David Jemibewon (rtd), on the issue. This is what he had to say: 

Can the former service chiefs be tried by civil authority like the EFCC rather than the military institution? 

A man, who retires from the armed forces, either voluntarily or otherwise, ceases to be a subject of the military laws. But if the offence for which is being tried was committed when he was still serving, that offence can be defined as military offence. It is only then he can be tried by the armed forces. In other words, if a man who had left the military; and when I say the military, I mean the Navy, the Army, the Air Force, he ceases to be a subject of military law except the offence for which he is being tried was committed before he left the mili­tary. So, if a former Chief of Naval Staff, Chief of Army Staff, Chief of Air Staff or any military officer for that matter, leaves the military either by voluntary retire­ment or whatever, he ceases to be a subject of military law because before a man joins the army, he is first and foremost a civilian. 

When he retires from the military, he reverses back to being a civilian. Even though he is a retired military person, he is subject to civil law as all of us are.

There's more in the full article. Gen. Jemibewon's position is that retirees can be tried in a military court only for offenses that were committed prior to retirement. A number of countries have such look-back jurisdictional provisions, but prevailing human rights standards disfavor the military trial of retirees and do not distinguish between pre- and post-retirement conduct.