There are a lot of US agencies which have law enforcement functions - with their own armed force and powers to search, detain, seize, etc. US Postal Service has

There are a lot of US agencies which have law enforcement functions - with their own armed force and powers to search, detain, seize, etc. US Postal Service has one, so does IRS, Department of Education, Library of Congress, and many other federal agencies. One could be surprised why the Postal Service is dealing with things having nothing to do with delivering mail, but mission creep is extremely common in all branches of federal government.