The abolition of slavery was made constitutional by what 1865 amendment?
Though Lincoln's Emancipation Proclamation ended slavery in the South, at a national level, the practice remained in a semi-legal state. So, in 1865, the United States ratified the 13th Amendment, which abolished slavery "within the United States, or any place subject to their jurisdiction." However, a line in the amendment seemingly grants an exception as "punishment for crime whereof the party shall have been duly convicted," which has raised flags in recent years.
Source: U.S. Senate