I had no idea, nor did I ever really think about people like the IRS Investigators who I know carry and have some pretty surprising LE power.
You might want to read about non-enforcement pocket commissions (the ID that a majority of IRS agents and collectors have). Basically what it boils down to is that a majority of IRS agents and specifically collectors have no enforcement ability whatsoever. Link
"Pocket commissions are categorized as either "enforcement" or "nonenforcement." Enforcement commissions conform to the format prescribed by the Department of Treasury for Treasury Law Enforcement Officers and may be issued only to individuals in the 1811 series, Special Agents (Criminal Investigation).. Nonenforcement pocket commissions are those issued to all other authorized employees."
The only reason they are able to accomplish anything is because most people are afraid when they even hear the mention of the IRS, that they follow along without question.