On Thursday, the Federal Criminal Court's appeals chamber in the southern Swiss city of Bellinzona confirmed the earlier ruling and the accompanying sentence of 20 years behind bars for Liberian Alieu Kosiah.
The appeal ruling also confirmed that after serving his sentence he should be deported and barred from re-entering Switzerland for 10 years.
Most strikingly, the appeals court judges agreed with the prosecutor and plaintiffs that a number of his actions also amounted to crimes against humanity.
That marks the first time anyone has been convicted of that most serious charge in Switzerland, made possible by a law change in 2011.
Kosiah lawyer Dmitri Gianoli hinted that his client, who pleaded his innocence and demanded an acquittal, would take the appellate decision to Switzerland's supreme court.
Kosiah, who settled in Switzerland in 1998 and was arrested there in 2014, "is very disappointed by the court's decision," he wrote to AFP in an email.
Questioning whether the verdict was "a political decision," Gianoli said his client would "examine all the measures at his disposal to reestablish the truth."
Kosiah's conviction by the Federal Criminal Court in 2021 marked the first time a Liberian was convicted - either within that nation or anywhere else - of war crimes committed during the conflict.
This ruling is "historic", human rights lawyer Alain Werner, who heads the NGO Civitas Maxima and represents four of the seven plaintiffs, told AFP.
"This is a great day for these incredibly brave Liberian victims who crossed seas to find justice, and obtain it in spite of Ebola at the beginning of the case, and Covid-19 at the end," he said.
"It is also a great day for justice and for Liberia."
In the 2021 verdict, Kosiah, now 48, was found guilty of a slew of war crimes committed as commander of the United Liberation Movement of Liberia for Democracy (ULIMO) rebel group.
He ordered or participated in the killing of 17 civilians and two unarmed soldiers, as well as rape, and deploying a child soldier, the court ruled.
He had also ordered lootings and repeatedly ordered, or had himself inflicted, cruel and humiliating treatment of civilians, and mishandled corpses, according to that verdict.
Thursday's verdict found that a number of those actions, including the murder of four civilians and incitement to murder of 13 others, amounted to crimes against humanity.
So far, only a handful of people have been convicted in Liberia itself for their part in the brutal wars, and efforts to establish a war crimes court in the country have stalled.
But a Paris court last November found another former Liberian rebel commander, Kunti Kamara, guilty of crimes against humanity.
Earlier this year, suspected warlord Gibril Massaquoi appeared in a Finnish appeals court accused of atrocities in Liberia's civil war, following his acquittal last year by a lower court.
Former Liberian warlord-turned-president Charles Taylor was convicted in 2012 by an international U.N.-backed court in The Hague of war crimes and crimes against humanity, but that was over atrocities committed in neighboring Sierra Leone, not in his own country.