Why is this case in the military justice system?

Sam Mednick of the Associated Press writes here that a former president of Burkina Faso has been charged before a military court with complicity in the murder of his predecessor. Why a military court?

Human rights jurisprudence strongly disfavors the trial of civilians in military courts and the African Charter of Human and Peoples' Rights forbids it entirely.

Add Burkina Faso to the list of states that violate this principle, such as Uganda, Egypt, Lebanon, and Pakistan.