The Buyer Management tool (available in "My eBay" under "My Account: eBay Preferences") gives sellers more control over who may bid for or buy their items. This feature helps to reduce post-transaction issues and potential unpaid items.
Buyer Management enables sellers to block bidders:
From a country not designated they will ship to in Sell Your Item (or other listing tools)
With a net negative Feedback Score
With two Unpaid Item strikes in the last 30 days
A blocked buyer can still request permission to bid or buy by contacting the seller. If the seller agrees, the buyer can be added to the Buyer Block Exemption List.
More control over where you want to ship
You are able to specify countries you do not want to ship to. For example you can indicate you ship to Europe, but specifically exclude Russia and Italy.
To do this, just follow these steps:
Click My eBay at the top of any eBay page
Click on the Account tab and select "Site Preferences"
Location Buyer requirements and click on the "Show" link to the right, then click "Edit".
Check off "Buyers in countries to which I don't ship"