ATF is an agency of the executive branch thru the US Treasury. Secret Service is Treasury also.
Thanks for note. However, not only is executive branch constitutionally required to faithfully make sure that all laws are faithfully executed as evidenced by Section 3 of Article II, but also consider the following. Regardless of which branch of federal government that ATF belongs to, the Supreme Court has clarified in general that powers not delegated to the federal government expressly via the Constitution are prohibited.
”From the accepted doctrine that the United States is a government of delegated powers, it follows that those not expressly granted, or reasonably to be implied from such as are conferred, are reserved to the states, or to the people. To forestall any suggestion to the contrary, the Tenth Amendment was adopted. The same proposition, otherwise stated, is that powers not granted are prohibited [emphasis added].” —United States v. Butler, 1936.
Also, regardless what FDR's activist justices wanted everybody to believe about the scope of Congress's Commerce Clause powers when they wrongly decided Wickard v. Filburn in Congress's favor in 1942, the justices wrongly ignored that a previous generation of justices had clarified that the states have never delegated to the feds to the feds to regulate intrastate commerce.
”State inspection laws, health laws, and laws for regulating the internal commerce of a State, and those which respect turnpike roads, ferries, &c. are not within the power granted to Congress [emphases added].” —Gibbons v. Ogden, 1824.
So if the ATF is regulating intrastate commerce in any way, then they have no constitutional authority to do so.