For USPS they have a list of verified hemp vendors, they tried a couple years ago to open packages suspected of marijuana without a warrant. The outcome was it doesn’t matter if they suspect it, you still have to get a warrant. So now if a vendor is a certified hemp vendor they can’t touch it. Now UPS and FedEx are private companies so they can do pretty much whatever they want, that’s why almost all hemp shipments go through USPS. I’m paraphrasing a lot but that’s the gist of it. USPS is currently and has been the largest drug dealer in the country, even with omitting hemp because with the volume they process you could never catch them all and every other drug doesn’t have a pungent smell like weed.