For example, the legislature in the State of Mississippi has exempted sex offenses (other than certain of those-type matters handled by Youth Court for Juveniles) from our laws regarding Expungements.  

The reasoning behind this exception is found in a recent Mississippi Supreme Court Case where a Defendant in 2011 pleaded guilty to the misdemeanor offense of disseminating sexually oriented material to a minor.   Chelsey Ferguson vs Miss. Dept. of Public Safety, 278 So. 3d 1155 (Miss. 2019)

The Court there pointed out that the Miss. Code Annot. Sec. 43-33-55 reads, in part: 

"Except for juvenile criminal history information that has been sealed by order of the court, this chapter exempts sex offenses from the laws of this state or court orders authorizing the destroying, expunging, purging or sealing of criminal history records..  Ferguson at Page 1158.  

The Court also stated that the legislature purposefully kept sex offenses out of the expungement possibilities  "in the interest of protecting vulnerable populations, and, in some instances the public, from potential harm."  Miss. Code Annot. Sec. 45-33-21

The bottom line is that sex offenses cannot be expunged,even if they are misdemeanors.