Is it possible to back out of a car contract after you have signed and left the lot with the car?

Is it possible to back out of a car contract after you have signed and left the lot with the car?
If you have signed the paperwork taking ownership of the vehicle legally it is yours once you drive it out of the dealerships parking lot. You can buy a GM certified vehicle and return it within 3 days or 150 miles with no questions being asked.