Jesse McCartney hat smoking cigarette shorts fred segal wine glass of wine white wine

Maybe he's channeling James Dean? Jesse McCartney played the rebel role while having lunch with a gal pal at Fred Segal in Los Angeles Sunday when he puffed on a cigarette ... directly in front of two no smoking signs.

The very casually dressed singer/actor sported a black tee, cut-off gray sweats, backwards baseball cap and bright red sneakers while not just smoking but also having a very animated conversation and sipping white wine at the L.A. hot spot.

We were surprised by the alcohol consumption until we realized that JMac is 24. Seriously, when did that happen?!