Masters swimming rules are laid down by FINA  (Federation Internationale De Natation Amateur), the world swimming sports organisation based in Switzerland. They govern swimming worldwide - Masters Swimming, Open Water Swimming, Diving, Water Polo and Synchronized Swimming.

In the 90's FINA provided an a6 sized, 400 page Constitution and Rules Handbook that was updated every 2 years. Haven't seen one for awhile but that's not surprising since FINA started posting the rules on their website.

If you are planning to visit or reside in another country and are looking for a team, the FINA website has a contact list of affiliations in practically every country; the menu heading is National Federations. You may find it more useful to Google specific country/city information if you want to make first contact.