As an armored transport officer, I can say with some sureity that carrying in a bank is illegal. While these are considered private property for tax purposes, their contents are federally protected.
In SC, the info provided with a CCW clearly states that banks are verboten. More to the point, any private establishment can, at it's choosing, place a sign in the window and expect it to be honored. Places like hospitals, banks, polls, churches and schools are automatically off-limits by mandate of law.
Of course, as my instructor so eloquently put it, "If it's concealed, how they gonna know?" I carry for my personal defense and will continue to do so until the stores/banks provide an equal type of security.
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When Reason Fails.....