Voters in four states approved ballot measures Tuesday to prohibit slavery as a punishment for crimes in their states’ constitutions. 

The approved measures in Alabama, Oregon, Tennessee and Vermont are victories for advocates looking for states to revise language in their constitutions that allow forced labor in the criminal justice system. 

Voters in Louisiana, meanwhile, rejected a ballot measure to ban involuntary servitude as punishment for a crime, with about 60 percent voting against it. 

The approved measures will not immediately change the states’ prison systems, but they could lead to legal challenges about prisoners being forced to work or facing sanctions or loss of certain privileges if they don’t. 

The 13th Amendment to the Constitution abolished slavery following the Civil War, but it allowed involuntary servitude as a punishment for a crime. Several state constitutions have similar text, leading advocates to push against those provisions and some to back updating the federal Constitution to amend the language of the 13th Amendment.  

Sen. Jeff Merkley (D-Ore.) and Rep. Nikema Williams (D-Ga.) reintroduced legislation in Congress last year to amend the 13th amendment to remove the relevant section and send it to the states. 

More than a dozen states still have language in their constitutions permitting slavery as a punishment for crime, while other state constitutions do not address the issue at all. 

Colorado became the first state to vote to remove the language permitting slavery in 2018, and Nebraska and Utah followed two years later. 

The Alabama referendum that voters passed removes language from the Jim Crow era regarding topics like segregated schools, poll taxes and bans on interracial marriage, according to the Birmingham-based NBC affiliate WVTM

Former Confederate states continued to use various laws designed to imprison and reenslave Black Americans in the aftermath of the Civil War and the abolition of slavery. State officials found ways to get around the end of slavery in imposing involuntary servitude as a punishment for crimes under laws that targeted Black individuals. 

Updated Thursday at 11:06 a.m. The Associated Press contributed to this report.