I hope you're not suggesting that FedEx is a government agency And, as insane as this may sound, you're best bet is really the U.S. postal service. By using FedEx or UPS, you're signing your goods over into their care, and they're free to open them. The post office, on the other hand, needs to obtain a warrant to dig in to any suspected packages. Not really worth the trouble for a little pot.
I've been wondering the same, if it was safe and how much is safe before I start towing the line? I want to mail myself some a hotel to avoid taking it through an airport. And what should I put it in? I was thinking a cigar box and then just putting a jar at the bottom of the box, seems like it would work. Any suggestions?