The World Government is a political organization comprised of the majority of the world at large, ruled by the Gorosei. The Marines serve as their primary military organization, headed by the Fleet Admiral, while the Cipher Pol operate behind the scenes, either through sabotage, reconnaissance, spying, espionage and/or assassination; their most powerful enemies are largely pirates and revolutionaries.
For that, they conducted transactions with slave traders to obtain entry into different countries such as Elbaf, to allow for a larger variety of "merchandise".
Nico Robin, in particular, spent her entire life running from the World Government, and everyone who she joined soon betrayed her for the bounty on her head, or found themselves against the Marines and other government forces.
While some people are beginning to question the motives of the World Government, the general public still trusts them and would tend to believe information from them.
The World Government is willing to eliminate innocent people and their own allies to prevent the possibility of negotiating with criminals or accommodating their demands.
This doctrine is the principle of Absolute Justice.