Q: Missing music

I tried looking for The Chronic from Dr. Dre on iTunes and it is not listed. 2001 was the only album of his listed. I do remember it was on the store in the past, as I bought Nuthin But A G Thang a few years back. I wanted to buy a few songs from him, such as Let Me Ride. Is there some sort of dispute with the label, or what's going on? Thanks.