They cannot take money out of your bank account.
They are doing that to me, right now, on a $27 purchase I made of some toner
cartridges a few days ago. When you sign up with paypal, I believe you are required to State a backup funding source. Previously, for me, that had been a credit card. But that credit card was canceled per my request and their action and a new one issued because of a fraudulent charge. Thus the credit card account they have on file is no longer valid. So they went to my secondary source, which is my checking account. They must have done as I have described, because otherwise the purchase would not have gone through.