There is some degree of international coordination under the International Telecommunication Union (radio waves don't really recognize national borders), but in

There is some degree of international coordination under the International Telecommunication Union (radio waves don't really recognize national borders), but individual countries still have leeway to make their own internal rules. There is also some international cooperation aimed at keeping people from stepping on each others toes (e.g. I cannot use part of the 70cm amateur allocation because I am too close to Canada who makes different use of those frequencies). That said, as far as I can tell, it seems rules adopted by a significant number of countries (or a number of significant countries) are likely to become international.