I fly a private VP-C registered aircraft which is based mainly in the Middle East and Europe. I have a JAA licence but it had to be validated by the Cayman Islands CAA which is just a simple paperwork exercise based on your home licence. However, if the aircraft is going to operate commercially eg FAR 121, based in another state then you would ALSO need to have your licence validated in that state as well, which may not be so simple, depending on the state concerned.
Hope that helps.
