There might be some large boned guys that might be able to pull it off. I have yet to see it though.
Having been in the industry, met most of the big names and seen many contests, you rarely find anyone under 15% with over 18 inch arms. Most of the guys that claim size have much higher bodyfat than they think. They believe they are lean, but are not.
I have 19" arms when I am big, 17.5" when I am 20% bodyfat, and about 16.75" when I am very lean.
My main point was that every Tom, Dick and Harry claims they have 20" arms, or a friend has 20" arms, yet when asked for a picture they disappear.
Having studied a lot of the research, the simplest method I have to guestimating potential arm size naturally is to add 10 inches to your wrist. This would be a good relatively lean goal. At 25% you might add 11" to your wrist size, and maybe up to 12 or 12.5" for 40% plus bodyfat.