Checking packages, with humanoids and other forms of robotics, it's possible that law enforcement will become efficient. Right now almost any package containing illegal substance will cross the US/EU without issue, that's due to human flaws, robots will be so much better at detecting stealth and so-on (also because Scent and Xray and so-on will be built-in them), the exact reason illicit marketplaces available on Tor exists is because of human flaws.