And they're on some blacklist preventing them from being hired in some other law enforcement jurisdiction role?

Any decent one they probably are, but many jurisdictions don’t have a choice of who they hire.

They just need bodies.

https://www.propublica.org/article/stebbins-alaska-cops-crim...

No, that requires decertification (revocation of their "police license"), which is fairly rare. Rarer than it should be, if you ask me.