Since the late nineteenth century, the Chinese state has modernized and remodernized its laws, courts, prisons, and penal camps. But certain criminal justice practices survived each wave of reform, including retroactive laws, punishments that differ depending on the societal status of the offender, the criminalization of political opposition, and the sentencing of convicts to hard labor. The labor-camp (or laogai) system became a signature institution of Mao's China and remains important, even though its population has been reduced. Its stated rationales were to reform idlers through work and to provide the state with labor; the reality is arbitrary and indefinite confinement under jailers with unregulated power. Mühlhahn describes prisoners' struggles to preserve pockets of individual freedom and identity under harsh, often fatal conditions. It is a system that post-Mao reformers, facing opposition from the Ministry of Public Security, have been unable to get rid of.