[googlryas]

You could argue that while they don't have police authority, they do do police work.

[gobengo]

In the past there have been legislative efforts specifically to separate international policiing from domestic policing in the US.

The purpose of https://en.wikipedia.org/wiki/Posse_Comitatus_Act "is to limit the powers of the federal government in using federal military personnel to enforce domestic policies within the United States."