the problem is that this shifts the burden of proof of innocence on you, instead of the burden of proof of guilt on the authorities. They can say "we have reason to believe you committed a crime to obtain this" and there's not much you can do except to prove them wrong. That goes against "unless you can prove I have a committed a crime, I have committed no crime". That's what I take issue with.
> Your portrayal of the police as an arbitrary force that seizes things without recourse is, I think, incorrect.
You're probably right. There is recourse and procedures, so not quite Wild West level lawlessness. But the system is very much rigged against you if for some reason the police believe (rightly or wrongly) that the assets were obtained illegally or used in illegal activity. And it very much facilitates police corruption since their burden of proof is so low -- who is to say that the police is wrong?