Originally posted by: Death BOO Z
I call this a plothole...
from what we've seen so far, the ANBU were guarding the villiage during the chunin 3rd exam, they looked for information and they're in charge of disposal of missing-nins....

that sound like the police for me, and seeing that Itachi was head of the ANBU, it even makes more sense...

I think the ANBU guys wear masks only when they go out on missions, but who knows...
Well, since the Uchiha clan was incharge of policing the city and was wiped out, perhaps the ANBU had to expand and take over the internal aswell as the external affairs of Konohas protection.