Is it a war crime to detain prisoners at blacksites and torture them? It seems like war crimes and ignoring the Geneva Convention are pretty common unfortunatel

Is it a war crime to detain prisoners at blacksites and torture them? It seems like war crimes and ignoring the Geneva Convention are pretty common unfortunately and if Western powers can refrain from doing them places like China or Russia will completely disregard them as well. It can't be a do as I say not as I do scenario.