It was not then clear under whose legal control a crime committed on plane was,..... Then係呢度係咩意思?

However, the man escaped punishment because it was not then clear under whose legal control a crime committed on plane was, the country where the plane was registered or the country where the crime was committed.

雖然如此,這名男生 沒有受到逞罰 因為 機上犯罪 的法治權,是屬於飛機所屬的註冊國, 在那時候 沒有規定清楚.

所以:
It was not then clear under whose legal control a crime committed on plane was,...

= 機上犯罪 的法治權,..., 在那時候 沒有規定清楚.

很奸詐的問題.It還故意大寫,讓星星以為是一句話的開頭.

要全句解讀，這個是不很清楚的。。。。。。

then, adv. at that time,then and there;used to call attention to express a question that "who has been legal controling that crime" ?The legal-right control belongs to the registrar "country of origin" of the airplane.