This is worded confusingly and the tweet text doesn't help at all, so to clarify: slavery is currently legal per the Oregon constitution (and the U.S. constitution) as a punishment for a crime. This ballot measure would remove this exception and make slavery illegal always.

RT @[email protected]

Slavery on my ballot in 2022

🐦🔗: https://twitter.com/interest_mild/status/1583960014418432000

Mildly Interesting on Twitter

“Slavery on my ballot in 2022”

Twitter
(In Oregon specifically, of course.) So if you're in Oregon and see this on your ballot, vote yes to abolish slavery for real this time!
For those outside the US wondering "why isn't slavery already illegal always," the answer as usual is "racism"