In response to several ramp inspections outside the territory of the European Union Member States, when the flight crew members were found operating aircraft registered in a Member State other than the one that had issued their pilot licences, ICAO amended the Annex 1 (Personnel Licensing) to the Chicago Convention on International Civil Aviation to enable, within a group of States, the automatic validation of licences issued by any State of the group when those States are party to a formal agreement under common licensing regulations.
The IAA issues all EU Part-FCL licences with the following remark on the licence at item XIII: ‘This licence is automatically validated as per the ICAO attachment to this licence (see IAA website)'. In this context ‘‘automatically validated' means the acceptance without formalities, by an ICAO contracting State listed in the ICAO attachment, of a flight crew licence issued by a State in accordance with Annex I to the Chicago Convention. The ICAO attachment can be downloaded here.
If you wish to fly outside the European Union (EU) in an aircraft registered in an EU Member State other than the Member State that issued your licence, you must carry the latest version of the ICAO attachment with you. This may be a paper or digital copy and must be carried in addition to your pilot licence. This ICAO document contains a reference to the ICAO registration number of the agreement for automatic validation and an overview of the countries that are part of this agreement (EU Member States, Switzerland, Norway and Iceland).