| Members | ||
 |
Belgium | Member since 1999 |
 |
The Netherlands | Member since 1999 |
 |
Luxemburg | Member since 1999 |
 |
France | Member since 1999 |
 |
Germany | Member since 2001 |
 |
Ireland | Member since 2001 |
 |
United Kingdom | Member since 2002 |
 |
Poland | Member since 2004 |
 |
Austria | Member since 2004 |
 |
Romania | Member since 2007 |
| Portugal | Member since 2023 | |
 |
Hungary | Member since 2007 |
 |
Croatia | Member since 2015 |
 |
Spain | Member since 2019 |
| Observers | ||
 |
Czech Republic | Observer since 2010 |
 |
Slovenia | Observer since 2010 |
