The heavy sentence comes as Jakarta boosts its troop deployments to Papua, the scene of a decades-long separatist insurgency.
Soldier Wahyu Insyafiadi received the life term on Wednesday for selling some 2,600 pieces of ammunition, including bullets, to rebels.
"(Insyafiadi) has tarnished the image of the Indonesian army," presiding judge Muhammad Idris told a military court on Saturday (Feb 14).
Two other military members were sentenced to two-and-a-half and 15 year sentences respectively for their role in the sales.
Papua is a mineral-rich former Dutch colony that shares an island border with independent Papua New Guinea.
Indonesia took it over in the 1960s following a vote to stay within the archipelago that was widely viewed as rigged.
Ethnically Melanesian, most Papuans are Christians who have few cultural links to Muslim-majority Indonesia. - AFP
Did you find this article insightful?