I was reading this interview with some CoD4 guys over at 1UP, when I found the following part:
GFW: You can carry only two weapons at once?
VZ: Yeah, you get one primary weapon — an assault rifle, submachine gun, sniper rifle, whatever — and a sidearm. Attachments work with pistols, too. Then there’s the Dual Wield [...]
"A CoD4 Disappointment" - 26.08.07