I recently tried to use a Visa debit card. Apparently, things were changed as of Aug 1. At least with the vendor of the card that I purchased. I went to a local supermarket where they have a rack of lots of different gift cards. In the Visa section, they had cards that were marked Domestic Use Only, and also some that were marked for International Use. I purchased a $50 and a $100 of the International Use ones. I made sure to register them, etc. The transactions for Attitude were declined. I called the number on the back of the card and they told me that the rules had changed. I ended up sending a money order via snail mail, and I did get my seeds. I'm not sure the Visa debit cards can be used any longer..or maybe it was just that vendor, dunno.
As for PayPal, it is not the seed banks who are the problem. PayPal will not allow it, and I have read that there have been incidents where PayPal closed vendors' accounts and confiscated funds etc. No idea if that is true, but it is PayPal who doesn't allow illegal transactions.