Katniss Everdeen, the protagonist of Suzanne Collins' The Hunger Games, commits three illegal activities. First, she leaves the boundaries of District 12 (her home district), something which is looked negatively upon. (The district is even encircled by chain-linked fencing with barbed wire atop it. At times, the fence is electrified.) Second, Katniss hunts once she leaves the boundaries of her district. Lastly, Katniss trades some of her illegally hunted animals to other people in her district for things her family needs.
Katniss needs to hunt in order to take car of her family. Also, hunting is something which allows her to be herself and escape from the poverty and problems she faces in her district. Hunting allows Katniss to remember her father as well. He was the one who taught her about the venomous snakes and safe foods to eat in the forest. She can remember her father and what he taught her when hunting.
The illegal activity Katniss particpates is hunting. She goes beyond the fence to hunt, and brings back the food to her family. She needs to do this because of the extreme poverty that takes place in district 12, where Katniss lives.