It is well known that non-renegotiable contracts with third parties may have an effect on the outcome of a strategic interaction and thus serve as a commitment device. We address this issue when contracts are renegotiable. More precisely, we analyze the equilibrium outcomes of twostage games with renegotiation-proof third-party contracts in relation to the equilibrium outcomes of the same game without contracts. We assume that one of the parties in the contractual relationship is unable to observe everything that happens in the game when played by the other party. We first show that when contracts are non-renegotiable, the set of equilibrium outcomes of the game with contracts is restricted to a subset of Nash equilibrium outcomes of the original game. Introducing renegotiation, in general, imposes further constraints and in some games implies that only subgame perfect equilibrium outcomes of the original game can be supported. However, there is a large class of games in which non-subgame perfect equilibrium outcomes can also be supported, and hence, third-party contracts still have strategic implications even when they are renegotiable.

This paper characterizes equilibrium outcomes of extensive form games with incomplete information in which players sign renegotiable contracts with third parties. Our aim is to understand the extent to which third-party contracts can be used as commitment devices when it is impossible to commit not to renegotiate them. We characterize renegotiation-proof contracts and strategies for extensive form games with incomplete information and apply our results to twostage games. If contracts are observable, then the second mover obtains the best possible payoff given that she plays an incentive compatible and renegotiation-proof strategy and the first mover best responds. If contracts are unobservable, then any Bayesian Nash equilibrium outcome of the original game in which the second mover plays an incentive compatible and renegotiationproof strategy can be supported. We apply our results to Stackelberg competition and show that renegotiation-proofness imposes a very simple restriction.JEL Classification: C72, D80, L13.

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