Hi, yes - the Swiss motorway tags are tricky so and so's to unstick - we tend to use a bit of masking tape to hold them in place rather than risk the untender mercies of the glues they use. IT is going to be a warm water and soapiness job. If it seems stubborn, you could wet some tissue and tape it over the tag to get wetness and soapiness into the right place overnight. It may take a few days, but that ought to lift it without doing damage.