Niles was a member of the Maquis.
In 2370, he was a member of the Maquis cell commanded by Calvin Hudson, a former Starfleet commander who became part of the Maquis. Wearing a Starfleet uniform, he was part of the Maquis team that captured Gul Dukat on Deep Space 9. He also took part with a Federation attack fighter in a Maquis raid on a weapons depot on Bryma which failed. (DS9: "The Maquis, Part I", "The Maquis, Part II")