It's best to have a relay with such lights so they draw power from the battery.
If you run the "Switched from power" to a accessory on source that only comes on with your key on. You will never leave those lights on and can use them auto on, OR on with switch depending on how you have the switch turned , on or off. This is detail of how to do it.
http://www.r1200gs.info/howto/relay.html
It would go like Bat short red wire to fuse and on to relay Terminal 30
Terminal 87 to the power to your lights,
85 to a ground, (Your Neg Battery terminal of frame ground)
Take power from acc source, and go to the one side of a switch and on to the terminal 86 on relay.

In this way.
Lights have no power with bike off.
Bike comes on with switch off still no lights.
When switch is turned on, Power comes from acc. on bike to term 86 and through relay to terminal 85 and trips "Breaker" in relay, that gets the power from the fused terminal 30 and completes the circut and sends power out to terminal 87, Giving your lights full and direct, clean power from the battery.

This is not the cheap way, it is the best & Right way. Cost around $25 in A water resistant relay, a switch (Any switch can be used as amp rating will not mater as relay takes the load) and wire plus a few terminals. It's a bike so following Boating guidelines is smart, get your parts to do this at a boating store such as west Marine or boaters World. They are more resistant to water and exposure.