The Appeal Court in Belgrade abolished a lower instance’s decision to rehabilitate a Chetnicks’ leader, Nikola Kalabic, due to a procedural fault, the court’s statement said on Friday.

The Higher Court in Serbia’s western town of Valjevo ruled last May to rehabilitate Nikola Kalabic, the commander of the Serbian Royal Mountain Guard Corps during the World War II, and the closest ally of General Draza Mihailovic, the supreme Chetnics’ commander.

But the Appeal Court found that there were some procedural mistakes and ordered Valjevo’s Court to correct them, mainly to establish if Kalabic was declared a war criminal and a collaborator with German occupiers and the way he died.

A law in Serbia stipulates that no war criminal can be rehabilitated.

After the WW II, the Yugoslav security service captured Kalabic, who then allegedly agreed to cooperate in a hunt for Mihajlovic in exchange for immunity.

His family denied the deal. Kalabic was reportedly killed by the partisans, but the place and the manner of his death remained murky.

Kalabic’s boss Mihailovic was rehabilitated in 2015. The ruling said that he did not have a fair trial after the war, that the charges were ideologically based, that he had no right to defense and that he met his attorney just before the trial began.

Chetnics were an elite unit of the former Yugoslav Royal Army, who stayed in the country as the national army after the initial command capitulated in 1941 .

Mihailovic and his fighters started as an anti-fascist guerrilla, but later switched sides and lost support from the Western allies which then turned to the communist and partisans’ leader Josip Broz Tito.