Avoid the Pissing Match!
See "Ranger's Comments" under the Rules & Regs section posted on the BLM Deso website-
-A spare lifejacket is not required by State Law, but itís a great idea to carry one.
So I would guess it is not enforceable, but why get into a pissing match with a ranger at put-in. Even if you are right, you are not going to win. I have first hand experience on that one.
Cataraftgirl is right, as is common sense. Take an extra per boat.
Don't Wanna Die Askin' for Another Chance