WASHINGTON (AP) — Voters in several states have approved ballot measures that will change their state constitutions to prohibit slavery and involuntary servitude as punishment for crime. The measures curtail the use of prison labor in Alabama, Tennessee and Vermont. And in Oregon, “yes” on an anti-slavery ballot initiative was leading but was too early to call early Wednesday. In Louisiana, a former slave-holding state, voters rejected a ballot question asking whether they supported a constitutional amendment to prohibit the use of involuntary servitude in the criminal justice system. Anti-slavery advocates celebrated the results as a signal for what’s possible in the effort to end the slavery exception in the U.S. Constitution.