Nearly 157 years after the 13th Amendment was ratified to prohibit slavery and involuntary servitude, five states will ask voters to decide on measures banning slavery — in the form of prison labor.

Advocates who petitioned to add such questions to the ballots in Alabama, Oregon, Louisiana, Tennessee, and Vermont hope to remove provisions in state constitutions that provide for slavery or involuntary work in the criminal justice system. The practical upshot would be to make prison labor voluntary.