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In the U.S., I think the reputable scrap metal yards have to ask where it came from. Some states have laws and also the businesses want to protect their reputations. But I'm sure it can be hard to recognize the origins and there must be some buyers who prefer not to know.

I think in this case it is the latter. Kind of like "waste management" in New Jersey. Don't ask, don't tell. I'd sure be asking questions if a van load of neatly rolled up lead showed up.