Not everybody who teaches Judo is affiliated with the USAJF, the United States of America Judo Federation, but lots of the Judo dojos in the USA are affiliated with it including mine, although I don't train in Judo at my dojo I train in Karate as my sensei teaches both Judo and Karate. As I am not a Judo student, I don't know everything about the USAJF but from what I do know, mostly from friends who train in Judo is that their ranking system works like this. Belt ranks are gained by competing in tournaments and winning, or senseis may promote students up to brown but a sensei may not promote a student to black, that has to be done by the USAJF and its done by performing well enough in tournaments. Once a student is a black belt Judo under the USAJF, they are a black belt in all Judo schools that operate under the USAJF so contrary to what this other poster said, that if you gain a certain belt rank in your dojo, be it black belt or whatever, that in all other dojos you're a white belt, this is not true at least for Judo students who train in dojos that are part of the USAJF. I think its good for the martial arts to operate under large organizations like the USAJF that regulate how the system is taught, including rank requirements. That way, you won't have students who get black belts just for eating their lima beans as this other poster pointed out in this other board which unfortunately in some dojos is true.