Casey Anthony may be in Columbus, OH this AM, and if she is ... she can get police protection, but it's going to cost her.

The Columbus PD tells TMZ ... they have a Special Duty program, which allows people in their fine city to hire off duty cops for protection, and that's what Casey would have to do if she wants someone to guard her from the angry mob.

We're told, however, if there is a specific, real threat ... the PD would treat her the way they would anyone else and provide appropriate protection, without cost.