Ok, I just flew back from Chicago with 10 bottles of Two Brothers beer in my checked baggage(two 12 packs minus the 2 bottles I drank in my hotel room). I checked the TSA's site and found this:
http://www.tsa.gov/travelers/airtravel/holiday.shtm which covers beer and says is should be checked, not carried on the plane, however it doesn't cover kegs.
However, as far as the transporting liquor across state lines, I didn't have any issues brining my beer from IL to MN. And my suit case full of beer was the first time I have ever had the TSA check my suit case. When I got it back my lock was missing and there was a note from the TSA(preprinted we opened your bag note). All of my beer was still there and nothing was missing, if it was illegal to cross statelines I have a feeling that would have been confiscated on the spot.
I am not a lawyer, but I don't think the crossing state line thing is applicable for personal consumption, maybe if you were crossing state lines with a truck full of beer to sell in your bar or liquor store......though I could be wrong.