Hi Dave, noted you're originally from the US, over there I think the SABCO kegs and others can be picked up a lot easier there from home brew stores and the like.
Here in OZ sadly it's a different story.
There are legal ones to be had but they are stupidly expensive.
KegKing sell them. But appears you need 10!
KegKing
Ebay currently stock quite a few, on castor wheels and at a crazy price:
Ebay Kegs
You can tell they're legal cos they're shiny! But shiny and new also equals expensive! So I can see your problem. We all have this issue and it is a common gripe in the homebrewing community.
On ebay the ones that display domestic brewery names get removed from sale. That is because they state they are the property of the brewery and no matter how old can be reclaimed and sold for scrap metal. I know they sell them for scrap as have tried contacting a recycler in Victoria's West to purchase one before it hits the crusher - and had no luck due to 'health and safety' concerns. They're worried you're going to try and repressurise them and won't sell them to you.
On ebay the only older kegs that seem to sell legitimately and not be removed have the names of european, UK and US breweries on the sides of them or are vintage XXXX kegs (I see these all the time and they are never removed unsure why). With the internationals I guess its because there's no one in this country hired by the overseas brewer to track down rogue kegs. And sending them overseas for scrap wouldn't make any sense.
If you're worried about legalities, then buy stock pots instead. A regular poster on here - Dommasura (beerbelly), sells a range of these as do some of the sponsors.
Hopper.
Edit- Just read Haysie's post - Yeah or you can get 'creative'!