Protected areas (PAs) have long struggled to successfully enforce compliance with their regulations. Even some of the best-funded PAs in the world face shortcomings in using enforcement as an effective deterrent to PA opposition. This suggests that traditional enforcement on its own may be insufficient for effective resource protection. Research was undertaken to understand why some would-be offenders refrain from harmful actions toward neighbouring national parks while others do not. Perceptions of the trustworthiness of PA managers were the most consistent predictors of exercised restraint on behalf of those living within the immediate vicinities of the Great Smoky Mountains National Park, Virgin Islands National Park and Podocarpus National Park. These trust assessments were most commonly based upon respondents' perceptions of positive personal interactions between PA managers and the public, of PA managers' receptiveness to local input, of the benefits and disadvantages associated with PA presence, and of PA officials' effective performance of their duties and equitable treatment of different groups. The study reveals trust and legitimacy as key factors related to voluntary compliance in situations where general agreement with PA regulations does not necessarily exist and provides insight into how trust and legitimacy can be developed or eroded.