But they don't ask, they tell you that you have to hand it over. You can appeal to the courts (which is an expensive option), but the judge may say the same thing and you have no (practical) choice . That's why I say that you don't own it -- if you owned it and the police ask for it, you could say "no".

What then, do I ask, do you own? Because it sounds like your answer is “nothing”, which is not a useful definition of “own”.

Can you hand it over if you don’t own it?

You can own your car but if you get in debt they can come and take it too. That's what living in country with other people is.