I have been bothered by the phrasing of the 13th Amendment since I first read it, in particular the bold:
Section 1. Neither slavery nor involuntary servitude, except as a punishment for crime whereof the party shall have been duly convicted, shall exist within the United States, or any place subject to their jurisdiction.
Section 2. Congress shall have power to enforce this article by appropriate legislation.
This is less clear wording than if the bold were omitted, but was it intended to allow for slavery to continue? Clint Richardson of RealityBloger claims that this allows private correctional companies to basically be slave labor sweatshops, and compares its legal status to that of marijuana:
Marijuana is illegal without a (state approved) doctors prescription, making it legal for state approved persons by state approved distributors.
Slavery is illegal without a judges (the STATE’S) prescription (permission), making it legal for state approved institutions to have slaves which are state approved (condemned) individuals.
Richardson claims a conspiracy between courts and prison companies, and make generally unfalsifiable accusations.
Jim Liske of USA Today wrote an article titled "Yep, Slavery Is Still Legal" which also asserts that slavery is technically still a legal punishment for convicts. He slightly contradicts his title at one point:
Importantly, Supreme Court decisions of the 20th century ensured that no one today is sentenced to actual slavery as a form of criminal punishment, but shades of Douglass' critique still ring true.
But he does not elaborate on which court decisions ban slavery or how.
In trying to determine when and how slavery was completely banned in the USA, I have come up short. Sources that assert that slavery is banned generally attribute it to the 13th amendment. Has there been any legislation or legal precedent that outlaws slavery in stricter terms than the 13th amendment? Are state governments responsible for banning it individually? Is slavery still legal in the United States?