The intergalactic Orion Wars started off as a war between two parties. They were the Empire on one side, and the armies of Light on the other. Later on, the Rebels also entered the scene, as a third party.
Some authors use "the black league" to indicate the troops of the Empire, while other authors -such as Lyssa Royal- refer to the Rebels as the black league.
"The Black League was an organizational resistance pattern developed during the Orion conflict, to counter the efforts of the Orion Empire, which was attempting physical and spiritual domination of the entire region. The Black League manifested not only as underground paramilitary Resistance organizations, but as a spiritual and philosophical orientation that manifested in many forms. These patterns have attempted balance in other planetary systems and are presently playing out on Earth through the human reincarnational cycle." (Lyssa Royal & Keith Priest, The Prism of Lyra)