Five year old thread.
Not sure why anyone who isn't growing commercial hemp would want these, but by US Federal law all viable hemp ceeds are illegal and considered "mari-juana". So without the appropriate permit/licensure you can't really buy viable hemp ceed legally anywhere in the USA. All hemp seeds you buy as feed are "supposed" to be sterile.
Most of the feedstuff is milled (crushed) or for people-food de-hulled so contrary to what's been written above, its pretty unlikely to be viable. I can't imagine that you can just buy a 50lb bag of untreated viable ceed over the counter anywhere in the USA, but that said, I don't doubt that a few individual beans from the "sterile" feedstock might germinate anyway.
I've heard (but never seen nor verified) that some kinds of commercial birdseed contain viable hemp se-ed, so that might be another option.
If you're willing to import it, there are probably a number of sources that would be happy to sell it to you. For example:
http://www.northcountryseeds.com/products/viable-hemp-seed
Obviously, if you live in the midwest or anywhere where there is feral cannabis (ie "ditchweed") you can find ceeds if you look for them.
And I'd imagine there are multiple places where you can get some within the USA (eg Etsy, Ebay, etc). Lets face it, if people are selling drug cannabis ceed, you must be able to locate non-drug cannabis ceed somewhere!