Three states on Tuesday voted to change their constitutions to ban slavery and involuntary servitude as a criminal punishment, while a fourth state opposed the change. Voters in Vermont, Tennessee, and Alabama all chose to curtail forced prison labor. The anti-slavery vote is also leading in Oregon, but the vote is too early to call Wednesday morning. In the former slave-holding state of Louisiana, however, a ballot question on supporting a constitutional amendment to end the use of involuntary servitude was rejected with 60.9 percent of the vote, the AP reports. The 13th Amendment of the U.S. Constitution, ratified in 1865, abolished slavery, but kept an exception to allow involuntary servitude as a punishment for crime.