Reversal of burden of proof going forward is good for collecting - retroactive is bad
As someone who both collects and has witnessed the smuggling and black market selling that happens in places like Bulgaria and how it's stripping these countries of their cultural heritage, I'm in favor of transparency and full documentation going forward (I'm in favor of the reversal of burden of truth going forward). Also because knowing the provenance of a piece adds value to the collecting community - we are interested in history after all - and requiring this of collectors going forward helps enrich all collectors/collections. But I agree going retroactive will do more harm than good.
kilde: