They have what every the law says, and for the US that's fifty different laws (plus a different federal law) and whatever the locals can get away with. You get to some of the backwoods areas of Tennessee, where the sheriff is the judges brother, and their cousin is the mayor, they can pretty much do what they want for a long time.
relevant sections of the article:
Rittenberry was housed with the men based on the physical.
"He still has male genitalia, and as far as the state of Tennessee is concerned and the jail is concerned, he's still a man," Denny said. "He will be treated like a man — with respect — but he has to be treated like a man because all documentation points to his male gender from birth."
Capt. Douglas Tackett, administrator of the jail and workhouse, said transgender people are offered protective custody if they have problems among the general population.
Rittenberry is in isolation for protection.
"In a facility like ours or any prison facility, when you have someone to fall in that category, he could be taken advantage of," Denny said. "He is in isolation to keep from being injured or someone hurting him."
Tackett said he doesn't remember having an inmate come into the jail with a complete sex change procedure.