I have just listed something so I have copied the options to show what restrictions I have placed on my auctions.

Buyer requirements
Block buyers who:
Are registered in countries to which I don't post
Have a feedback score equal to or lower than -1
Have received 2 Unpaid Item strikes in the last 30 days
Have bid on or bought my items in the last 10 days and have met my limit of 4 who have a feedback score of 5 or lower
Don't have a PayPal account
Have no credit card on file

Change buyer requirements