Some time in the not so distant future, man has colonized the solar system. The old nations of earth as we knew them are gone, but new ones (and perhaps some old ones?) have arisen to take their place. Many more are extant amongst the planets, moons, and other bodies of the system. Now, at some indeterminant place on Earth, their leaders, or representatives thereof, gather together to discuss the issues of the day.
(Check your RL politics at the door, imaginary new powers or resurrected old ones, only. Who will you be? Lord High Mugwump of Halley's Comet? Bretwalda of the Jovian Moons? Arch-Anarchist of Antartica? Emperor of Byzantium?)