This dissertation consists of three chapters about enforcing collective property rights systems. In the first chapter, we analyze how public co-enforcement affects a collective property rights regime's success. In the second chapter, we consider the problem of managing and defending the commons when common-pool resource coalitions form endogenously. We conducted experiments in the field with members of areas managed under a collective property rights system. Lastly, in the third chapter, we develop a method to estimate the direct effect of monitoring effort on non-recorded extraction (i.e., illegal extraction) of a natural resource. Each chapter has been designed around the territorial use rights fisheries (TURFs) management scheme implemented in Chile to enhance small-scale fisheries' sustainability.