The case is L.M., Jr. v. State, 600 So.2d 967 (Miss. 1992). The case dealt with 3 minors having a concealed weapon in their car. Their conviction was upheld on appeal.
The justices looked at MS statute for concealed weapons
97-37-1
(1) Except as otherwise provided in Section 45-9-101, any person who carries, concealed in whole or in part, any bowie knife, dirk knife, butcher knife, switchblade knife, metallic knuckles, blackjack, slingshot, pistol, revolver, or any rifle with a barrel of less than sixteen (16) inches in length, or any shotgun with a barrel of less than eighteen (18) inches in length, machine gun or any fully automatic firearm or deadly weapon, or any muffler or silencer for any firearm, whether or not it is accompanied by a firearm, or uses or attempts to use against another person any imitation firearm, shall upon conviction be punished as follows:
Chief Justice Lee, in the concurring opinion, made the remark ("[A] revolver carried in a holster on a man's hip was a partially concealed weapon. Conceivably, carrying a revolver suspended from the neck by a leather throng could be partially concealing it."). This was all it took for even lesser morons to stretch that to it's breaking point and beyond.
http://www.natchezdemocrat.com/2010/03/28/open-carry-gun-laws-trigger-discussion/
Adams County Sheriff Chuck Mayfield said “partially concealed” allows for holstered weapons, since the holster would cover a portion of the gun.
This allows law enforcement in Mississippi to stop anyone they see open carrying and harass them for ID and permit. For serious anti-gun law enforcement, it even lets them lecture them on their 'permit' means only concealed (like their previous partially concealed statement was totally forgotten), and some have even been cited for it. These charges are almost always dismissed before trial so as to ensure that the case law from 1992 isn't overturned, making a holstered openly carried handgun a clearly established right in the state.