See also The Phoenix Guards
Although at the time of The Phoenix Guards, and Khaavren's initial enlistment into the ranks of the guard, calling the Phoenix Guard "police" was seen as an insult, by the time of Five Hundred Years After, the organization had in fact become such.
Broken into two parts, the White Sash Battalion and the Red Boot Company, the latter division became the elite protectors of the emperor and the former became a much larger police force. The rivalry between the two groups can be fierce, though there is at least one example, Thack, of a soldier transferring between groups.
There is also a special division of the guard known as the Special Tasks Group who are responsible for surveillance and covert operations.
Phoenix Guards are known in Jhereg slang as "birds," due to the phoenix being a bird. Jhereg usually find Phoenix Guards will take bribes in regards to small matters such as unlicensed gambling. No matter how dire a Jhereg's situation, he should never attempt to fight or kill a Phoenix Guard, as that is much more trouble than it's worth.