LED Underglow installation

[FILESON]

Hello!

I'd like to install an LED underglow on my bmw but I have some difficulties in understanding how to install it due laws and restrictions there are in Denmark. The law says that if I want to have an underglow and want to connect the main controller to the battery, I have to connect it by a relay first and then to the battery, so that the lights won't work when the engine is running. My question is, if there is any fuse which delivers 12V but does not work when the car is running? Or is there any other option? When it comes to electricity and electronics I'm totally blank.

I couldn't find anything on danish forums so I decided to try here

Thank you for your time

[shogun]

We do not know the regulations in Denmark. But my understanding is that the underglow will only be on when the engine is off, see this, terminal 15 Terminals 15, 30, 30g and 30g_f explained (car accessories installation) https://www.youtube.com/watch?v=3JB44a5c3RQ