The U.S. Postal Inspection Service supports and protects the U.S. Postal Service and its customers by enforcing the laws that defend the nation’s mail system from illegal or dangerous use.
One interesting little fact from history is that the Postal Inspection Service was one of the first bulk buyers of the Tommy Gun (Thompson submachine gun).
i was once visiting a friend who worked at the US postal service. i was traveling with a backpack with gear that looked rather rough, ready to go hiking in the woods. at one point my friend took me to his office while i was in full travel gear. in the elevator he told the others that i was one of those people delivering mail in the american backcountry.
The federal government increasingly is finding interesting nooks and crannies to shove enforcement into. Customs and Border Protection is now larger than the FBI, and ICE which houses "homeland security investigations" is almost half their size. These, and other arms of government, are increasingly being used to clamp down on activity by citizens deep within US borders (such as the recent Portland riots).
Another interesting example of the phenomenon you describe is that until 2003, the Secret Service was part of the Department of the Treasury, as the agency was founded in 1865 to combat the then-widespread counterfeiting of U.S. currency.
And yet this same government randomly, arbitrarily, (or sometimes not at all) chooses to selectively enforce (or not) a wide variety of existing laws, all while busily making more new laws that may or may not be arbitrarily and randomly enforced (when / if it suits their current "agenda of the day"). It's gotten downright ridiculous, honestly.
What do they have to do with ebooks???