The conjunctive weight function is an equivalent representation of a non dogmatic belief function. Denoeux recently proposed new rules of combination for belief functions based on pointwise combination of conjunctive weights. This paper characterizes the rules of combination based on the conjunctive weight function that have the vacuous belief function as neutral element. The main result is that the unnormalized Dempster’s rule is the least committed rule amongst those rules, for a particular informational ordering. A counterpart to this result is also presented for the disjunctive rule.