Are they usually unique countrywide? Worldwide?
Just little off topic, but I had to look in to it few months ago and there are bunch of shitty resellers that sell individual codes.
It looks like good deal but when you need to put it on more than 10 unique products then it is better to register as manufacturer. The basic tear is ~40€/year and you can create 5000 codes.
And yes at least in EU they are managed by one company that then allocate them to countrys.
Edit: I refer to EAN specifically, shops usually requires them.