remery said..
Decrepit is correct, a Golf with push button start will unlock while the remote is in a metal combination surf lock. Being push button the thief could drive away. It didn't unlock when sitting on the rear bumper but I'm not prepared to risk it.
With my 2003 Elgrand, if you remove the battery from the remote fob the keyless entry/keyless start no longer works and you need to start the car with the mechanical key that is inside the fob.
I think most (all?) these systems need the fob to reply to a signal from the car, so without a battery it can do nothing, and they generally include a way to start the car if they fob battery is dead. On the Elgrands its easy, but I am not sure about Golfs.