If you are talking about someone doing a chargeback on a Bitcoin sale, then you're out of luck.
To be eligible for PayPal Seller protection, you must meet all of the basic requirements listed below under (a) Basic Requirements. To be covered for Item Not Received protection, you must meet both the Basic Requirements and the Item Not Received Additional Requirements listed below under (b). To be covered for Unauthorized Transaction protection, you must meet both the Basic Requirements and the Unauthorized Transactions Additional Requirements listed below under (c).
Basic Requirements:
You must ship the item to the shipping address on the Transaction Details Page.
You must respond to PayPal's requests for documentation and other information in a timely manner.
The item must be a physical, tangible good that can be shipped.
Your primary residence, as listed in your Account, must be in the United States.