In Mississippi you need a permit to carry openly under state law. The fact that state law violates the state constitution is another matter.
Thank you for serving.Miss. Code §§ 97-37-1 & § 45-9-101 operate together to ban carriage of a handgun "concealed in whole or in part" unless the carrier is inside a motor vehicle or possesses a License to Carry a Concealed Pistol or Revolver. As the Mississippi courts have said that a handgun in a holster is concealed in part, a License to Carry a Concealed Pistol or Revolver is required to openly carry a handgun in a holster in Mississippi.