Thanks to FeFe, I just read, that Paypal is supervised by the bank supervision of Luxemburg.
If they e.g. freeze your account, you can address a complaint to:
Commission de Surveillance du Secteur Financier
110, route d’Arlon
L-2991 LUXEMBOURG
Tél. : (352) 26 25 1 - 1 (central)
Fax : (352) 26 25 1 - 601
E-mail : direction at cssf.lu