I went to a house this evening for a showing and encountered a situation involving the basement lighting that I'm almost certain violates at least one part of the NEC. The house was built in 2000. The basement is finished with the exception of a utility room containing the HVAC, water tank, all of the plumbing stacks, and the main service panel. If it matters at all, we're in Wisconsin.
The basement has 3 total light circuits: a single socket in the utility room with a pull string, a pair of pot lights in the area ~15' from the stairs with a switch on the far wall, and 6 pot lights in the main area near the stairs with a dimmer switch on the wall immediately opposite the staircase.
The pair of pot lights far from the stairs were only affected by the nearby switch. The utility room socket, and the main area lights however, were only operational if the switch at the top of the stairs was on. The utility room and main area circuits did not affect each other thankfully, but as soon as you hit that switch at the top of the stairs both circuits were dead.
Based on what I know of the NEC from lurking on this SE, I believe that there are supposed to be lighting controls at the top and bottom of the stairs that work no matter what state the other is in; and that rooms are supposed to have lighting controls within x feet of the entrance of the room, and that the top of the stairs does not count as the entrance to the room for the majority of the basement; and that a room's lighting (like the utility room) shouldn't be controlled from the opposite end of an adjoined room.
We passed on the house for other reasons, but I'm curious as to how wrong this setup actually is, and given the behavior of the circuits, if it could even be fixed without running new wire.