My son has a 2001 Jeep Wrangler and his interior lights come on when he makes a left hand turn....go out when the car is going straight again. What's up?

Sounds like his flux capacitor is going out.

Door switch?

Sure sounds like something in the steering column. Is his left turn signal on when this happens, or happens every time the wheel is turned left with the signals off?

I did have a '78 Magnum, where the interior lights would come on when you pressed the brake pedal (and the brake lights did not work). Turned out to be a bad fuse in the brake light circuit, happened more than once. Replaced the fuse and brake lights worked normally.

Could be the door switch also if the door is loose/ wiggling. Has he had the doors off recently?