[Xylakant]

Well, you'll not go to jail, but underfloor lighting is strictly speaking illegal in germany and only allowed for show cars - and even then it has to be off on the road. (StVZO §49a Absatz 1)

Violating that rule invalidates the permission to drive that car on a public road, immediately voiding insurance coverage. You'd better not have an accident with that car, because you're personally liable for any damage caused. That might not bring you to jail, but can seriously ruin your life if you cause a permanent injury to someone else.

[Alexx]

Yes, specific requirements differ from country to country, and invalidating your insurance and crashing your car anywhere in the world has that effect.

Point is that you won't 'go to jail in the entire EU', or anything of the sort for simply driving car with an unusual load on the roof rack.

[mschuster91]

Oh, cops certainly do have the right to tow your vehicle and take you to the next police office, where you spend maybe 2-3 hours of processing. I can tell you, it's a boatload of bureaucracy and they won't let you out until it's all done.

[Xylakant]

They can also impound your vehicle, depending on the modifications and their mood. I used to ride heavily modded motorcycles - all the entries would need a second sheet in the papers. That was always great fun to see the traffic patrol compare serial numbers for air intake, exhaust, lights, indicaters, ... especially when it was wet and they had to crawl on the ground.

[mschuster91]

Hahaha :D One beer on me, my friend.

[Alexx]

That has nothing to do with going to jail, nor the EU.

A whole load of both public and private organisations have the right to tow your vehicle for many, many things, like simply parking in the wrong place, and you have to do the paperwork.

At this point you're essentially just arguing that if you break you countries local laws you have to deal with the police... mmm.