Any number of people can play in the league. To start one person needs to moderate the progress of the league, this person shouldn't be involved in the games as it would create a conflict of interest. The moderator needs to obtain a world map, and mark out each of the cities (with a pin or some other type of marker.) that the camarilla control (IE: Chicago, Brussles, etc.).
The object of the league is for a single person to take control of each city. Initially, the moderator will choose the first city that will be up for control. If the moderator so chooses he may allow multiple games to be played at once, but this could cause tactical problems as the controller of the city that's up for control must be present in the game. Multiple games at once are more possible at the start of the league when there are few controlled cities.
The league players will play for control of the city, the point system will be used and the player with the most victory points will take the city. The winning player (the one with the most victory points), will decide the city where the next game will take place, the chosen city can be one already controlled by another player (this is one way of taking over a controlled city.). As stated earlier, if a controlled city is attacked in this manner, then the controlling methuselah must be in that game (to defend his turf, of course.).
Aside from a city's controlling methuselah, the other players in any one game should be randomly determined, and each player in the league should play an equal amount of games. It is the moderator's job to make sure these conditions are met. (Be sure to be nice to the moderator, he's got the crappy job. ;)
Deck construction is unrestricted, unless the area plays with specific deck construction rules, make sure that everyone in the league agrees on deck construction terms at the start. Players who break the deck construction rules should be removed from the league. The only exception in deck construction is the number of princes a methuselah can have in his or her crypt. You can only play with a prince of a specific city if you have taken control of the city where that prince rules. The same goes for Praxis Seizure cards, a methuselah can only play a Praxis Seizure for a specific city if that methuselah controls that city. Justicars and primogens are not limited in this manner. Unless everyone disagrees, players should be able to change their decks at any time during the league, except (of course) during a game.
The first player to take control of every city (or if there's a time frame on the length of the league the the person who has the most cities) is the winner.