nealtw
Contractor retired
1. Turn off breaker to Light Circuit. Or suspect breaker circuit(s).
2. Confirm there is no power to switch terminals. Disconnect switch. Confirm there is no power to suspect pair of wires to exterior lights.
3. Remove exterior light(s) to access wires. Confirm there is no power to actual wiring at the light(s).
4. With suspect wiring disconnected between both the switch and light(s) with no live current, wrap the black and white wires together at the light fixture. Set your DMM to continuity or OHMs. Probe the suspect black and white wires in the switch box. If you have a reading of .06 to .08 ohms you have continuity (or you hear an audible beep). If there's a red wire in the light fixture, also test this method with the red wire.
That's nice. You know what, when the light doesn't come on with the switch.
There is one thing we know for sure there is no continuity.
We also know that if these lights work they are against code.
So the question will be, what to do to make it code but first you have to know what has been done. We can not cover all the what ifs in one paragraph especially with the experience of the OP.
So let's take it step by step.