I think whether it was his or his girlfriends is irrelevant when it comes to CCW rules. Seems to me it’s similar to having an open container - doesn’t matter if the driver or passenger is holding it - it’s open, so the responsibility falls on the driver, yes?
What about boyfriends, girlfriends, acquaintances, coworkers or uncles who opt not to say what is in their pockets before getting into your car? Do you search everyone before they get in your car? How would you have any control of that?