Earth is ruled by a single inoffensive and reasonably unopressive government. The solar system has been colonised; Mars has been terraformed, and Venus has been changed to the point where semi-permanent human colonies are possible. Beyond the asteroids, there are huge self-sustaining habitats in orbit of the gas giants. Sublight "Rieder-Janetzki" drives allow travel between planets in weeks or even days.
Earth (Population: 250,000) still suffers from the lingering after-effects of the pollution from pre-unification times. Civilisation is limited to a narrow band in the southern hemisphere, and the only decent food supplies come from Mars' gardens. Terraforming technology is improving the situation but without the knowledge that the Jovians have, only so much can be done about the radiation.
Mars (Population: 100,000) has been inhabitable to plant life for a lot longer than for animal life, and with fertilising compounds harvested from Venus' atmosphere it now grows enough food and petrochemical crops to feed everyone in the union. The population is a mixture of hardworking farmer/engineer types in towns and effete, artistic retirees in houseboats on the canals.
Venus' (Population: 1500) inhospitable conditions have been improved somewhat by 300 years of atmospheric seeding. Mining stations now exist on the surface, replacing the costly aerial harvesters, and Venus is providing an unexpected wealth of rare elements, as well as the basic building-blocks of life needed by Mars.
Slightly less than a hundred years ago, around the time at which the terraforming of Mars was completed to the stage at which people could walk around unaided and work began in earnest on Venus, the habitats around the outer worlds broke away from the Terran Union, and there has ever since been a state of cold war with the Jovian League. No shots have been fired as of yet, but the Jovians are fond of broadcasting bold claims from their capital on Ganymede; They say they have a sensor net which will detect any ship which attempts to come further out than the Asteroids, and that they will destroy any such ship, and they say that any attack on their territory will lead to all-out war. Rumour has it that they somehow keep the Earth poisoned, contaminating the water supplies and broadcasting subversive thoughts into the minds of honest Terrans, but nobody believes that sort of thing, do they?
Both governments claim the Asteroids as territory, though neither police them, and there is at least one known ring of smugglers who have taken people across the border - including, it is rumoured, some of the brightest scientists in the Union. It is also a route into the Union for Jovian spies, against whom the employees of the Terran Enforcement Agency must always be vigilant.
Three years ago, the Jovians sent a generation ship out to Vega, sparking a technological race to acheive a warp drive, in which the Terrans have the advantage thanks to their mine at Ilithyia Mons on Venus, which provides Besterium, an ultra-heavy element whose properties indicate its structure extends into hyperspace. These mines are the Union's most prized posessions, and the Jovians would do anything to get their hands on them.
You are a member of the Terran Enforcement Agency's Special Operations Unit - a highly-trained and well-funded if somewhat inexperienced team of Enforcers whose existence is only really justified by the paranoia of the Terran people. Still, if they're paying you this much to shoot hi-tech gadgets at targets and play zero-g air hockey, who's complaining?