the rule is simple you can't have more than 2 lights (not counting park lights) illuminating the front of the vehicle for regular driving, obviously high beams is different here.

ok the simple way around this would be for manufacturers to wire fog lights so they come on automatically when you have the lights in the first position, turn off when you have it in the second position ie low beams and then they come back on when high beams are enabled.

if you really need fog lights in actual fog you are supposed to turn off low beams and high beams anyway so the above approach covers all situations.