On Aubin's Veto Mechanism: A Survey

We revisit Aubin's veto mechanism—known as the fuzzy veto—in which agents may participate in a blocking coalition with only a fraction of their endowments, and show that its Core‐Walras equivalence stems directly from the classical Debreu‐Scarf and Aumann theorems. We first demonstrate that the Aubin core coincides with the set of Edgeworth allocations and, hence, with the set of Walrasian allocations. By modeling any n $n$‐agent economy as a continuum economy with n $n$ types of agents, we prove that Aubin's result is a particular instance of Aumann's Core‐Walras equivalence for atomless economies. We then incorporate the contributions of Schmeidler, Grodal, and Vind and translate them into Aubin coalitions in finite economies, showing that the grand coalition in which each agent contributes almost all of her endowments, suffices to eliminate every non‐Walrasian allocation. We also prove, in the case when the number of agents n $n$ greatly exceeds the number of commodities m $m$, that coalitions involving few agents (at most 2 m $2m$), characterize the Aubin core. Finally, we characterize Walrasian allocations as precisely those that are robustly efficient. This analysis unifies several critical strands of the core literature and clarifies the foundational role and interpretation of Aubin's mechanism in general equilibrium theory.