The immediate cause of the Gunfight at the OK Corral was that the Cowboy contingent had refused to check their firearms at the marshal's office as required by ordinance.  Up through the 1960s it was generally accepted that local jurisdictions could regulate both open and concealed carry in public places.  Then two things happened: 1) cities started passing tight restrictions and outright bans, 2) and the laws started getting enforced against whites.  Certain elements of the citizenry were outraged, the NRA happily started a campaign to reinterpret the 2nd Amendment, and eventually the black-robed fascists on the Extreme Court obliged.