Welcome to Harrak (The Calamitous Bob, #4)

Ex-soldier and new witch Viv has led the exiled Kazarans in the recovery of their city. Now victorious and saddled with pesky concepts like 'democracy' and the 'rule of law', she has prepared for the return of the humiliated Prince Lancer for he cannot afford to let her live. The enemy army is strong, but she is ready, and with the knowledge of earth's guerilla warfare, the power of friendship, and a genocidal golem, the foes will have much to contend with if they even want to reach the city.

After all, it's not a war crime if there are no war laws.