The whole thing. The cops asked both occupants of the car to step out, and the occupants cooperated fully. This separated them from the gun. After that, there was no reason whatsoever for the cops to take the gun - doing so, did not increase "officer safety" at all.
There was never anybody in the back seat. In fact, when the cop took the gun from the floorboards, there was no one in the car at all, and the gun posed ZERO danger to anyone.
WHen the cop decided to take the gun, and took it, he was unaware that the passenger had a felony conviction, or even that the gun was his. Both occupants of the car cooperated fully, and were completely non-threatening. No dangerous or threatening actions ever occurred, either before, during, or after the traffic stop (for expired tags).
The cop had ZERO reason for taking the firearm. Not the sightest. Except, "Oh, there's a gun there." And the 2nd amendment was written for the exact purpose of forbidding a government agent from taking away the gun under such (completely innocent, non-threatening) circumstances.
I've asked before: If the 2nd was not written to prevent that kind of seizure, what WAS it written for?
No one has answered.