I never asked. Since all of his accounts are denominated in USD and based in the US, I assume he filled out and returned a credit card authorization form (and just ate his card's 3% foreign transaction fee).

Interesting. I know non-EU people end up in messes when they get a speeding ticket for their rental car and can't exactly IBAN/SEPA money over in 5 minutes or less.

I went with the next best option: Ignore it, but it was more of a "warning ticket" that they could investigate further and issue a real ticket if I didn't pay.