Before all the pessimists chime in about if they want it, they'll get it...........
An easy way is run a wire from the points side of the coil to a hidden switch then to ground. The downside is if they leave their hot wire on when they walk off it may burn up your wiring before it burns out the ballast resistor.
Another way is a battery disconnect switch. But if you have an exposed battery, like in a Task Force or later, they can see it and jump around it with a jumper cable.
