DuncanMac -
Essentially, I agree with you. In the U.S. government system a lot of the justification is max budget expansion. This is partly due to basic need and partly due to a slush fund to 'borrow' from when the budget is exceeded.
However, these agencies have been over the line for a long time. For example, the ATF showed up with an Army in Waco to deliver a search warrant to protect kids in the Davidian compound. The child abuse question had been previously cleared.
(That was in Texas, wasn't it?)
Etc.