Abundant evidence suggests that high levels of contributions to public goods can be sustained through self-governed monitoring and sanctions. This experimental study investigates the effectiveness of decentralized sanctioning institutions where punishment opportunities are restricted to agents who are linked through alternative punishment networks. We find that the structure of the punishment network significantly impacts contributions to the public good, but not overall efficiencies. Contributions collapse over decision rounds in groups with limited punishment opportunities, even if the absolute punishment capacity corresponds to the complete punishment network where all agents are allowed to punish each other. However, after allowing for the costs of sanctions, efficiencies are similar across the different networks that allow for punishment and the no-punishment network.