From what I'm reading, he's running a raffle across state lines... I believe that also qualifies it as a federal issue... at his site, he places a value on the prize of $1,400 +++ free airfare/shipping. Use that amount, + the value of shipping, when filing your complaints to the appropriate authorities. If you state free puppie, authorities won't know the value.
He's using the internet, $20 entrance fee, $1400 prize, if you mailed your $20, USPS may be involved but def still federal because it crosses state lines... FBI comes to mind.
If you are at the point that you believe he will never honor his obligation, submit your complaint to the biggest dog on the block. You probably won't receive your pup but, he may face legal challenges that will cost him much more.
How to Report a Scam
He's running a raffle on the internet, there's just no way his operation can be legal! The gambling outfits have reams of legal requirements to do so.