The European Union is a group of 27 countries. They form a kind of club with members.
The members have lots of agreements to help them work together.
But many people say this is not enough. They want one rule book to set out what all the members can and cannot do.
This rule book is called the European Union constitution.
However, the set of rules will only become law if all 27 members agree to it by the end of October 2006.