US tariff arbitrage drains London copper; a White House exemption unwinds it 1 Tariff incentive 15% Jan-27, 30% in 2028 4 Vulnerability ~15% chance tariff starts 2 Arbitrage flow LME - London registered stocks 214.5 kt -14% by Aug 12 Atlantic lane 15% open US - COMEX deliverable stocks US customs stockpiled record imports expired shorts bid
3 Backwardation / squeeze steep

one-month spread stays steep as shorts bid for scarce LME metal

5 Unwind - COMEX premium wide

US premium carries the 15% tariff wedge