The FIFA Statutes and the accompanying regulations governing their implementation form the Constitution of football's international governing body.
I was just going through the FIFA Statutes, while debating why Britain should really get a unified team to have any real chance of regaining the World Cup (which they won't do: their loss!).
The "special status" granted to the Home Nations is huge:
- they get to have 4 different leagues at the national level, a privilege that no other nation can have;
- they get to appoint 4 of the 8 members of IFAB, the institution that makes (and changes) the rules. So basically no rule can be changed without British approval!
- they get to appoint one of the 8 vice-presidents on the Executive Committee, at the same level as UEFA, CONMEBOL etc. So they are basically considered at the same level of the biggest football organisations when there's anything to be decided.
This said, they are hopeless at diplomacy, pretty much like Italy, with the result that for decades UEFA has been dominated by a French/German/northern countries block, and FIFA by south-American alliances with marginal federations.