MN law states that: Private establishments - if posted or if personally requested to leave by the operator because that establishment bans guns on premises.
Places of employment, public or private, if employer restricts the carry or possession of firearms by its employees.
MN has specific laws about the posting as well:2) "Prominently" means readily visible and within four feet laterally of the entrance with the bottom of the sign at a height of four to six feet above the floor.
(3) "Conspicuous" means lettering in black arial typeface at least 1-1/2 inches in height against a bright contrasting background that is at least 187 square inches in area.
(4) "Private establishment" means a building, structure, or portion thereof that is owned, leased, controlled, or operated by a nongovernmental entity for a nongovernmental purpose.
So if the employer has a sign that meets the states sign standards you will be prosecuted for carrying illegally and most assuredly for homicide. It happens all the time. If you kill someone with or without a CCW you will always have to prove it was justifiable.