AVO

Advanced  Vanguard  Observations is the Vanguard's sect of investigations. They investigate supernatural crime when it may be related to vampires, who can actually be affected by law. Demon crime is mostly a "Hunt and kill", so AVO does not bother. It may even be known to represent some vampiric clients if they're shown to be trustworthy, especially via mindreading or telepathy, but evidence is unavailable for court. That's where AVO comes into play.

(To compare: They're basically the FBI/CIA, specific to Vanguard operations).