Feed them sugar water. It takes a while, but the colony will collapse from lack of nutrition. Sounds crazy, but it works, I've tested it myself.
The ants will continue returning to the supply of sugar and feeding their young with it... after a few weeks you will start seeing some ants that are lighter in color compared to others, once that happens collapse is not far away.
The best part is, the nest areas won't be recolonized by other ants for quite a long time.
Just set small dishes outside and keep them clean and filled, the ants will find them in short order.
