<p>Rapid growth in the use of drones potentially delivers significant economic benefits, but it has also given rise to considerable public concern about safety risks, infringement of privacy, and other unwelcome surveillance and observation. Drones are able to be operated remotely from the pilot, making it difficult to identify the operator and attribute liability for harm caused. This in turn means that existing regulatory frameworks might not induce an efficient level of drone-related harm. The first substantive chapter of this thesis considers measures to address concerns about privacy and surveillance. I propose the adoption of a package of measures including: tort law reform, the promulgation of a "Code of Practice for Drone Operations" under New Zealand's Privacy Act 1993, a remotely-readable identifier to identify approved operators, provision for aerial trespass by unmanned aircraft, provision for the destruction of unmanned aircraft committing trespass, and the clarification of what constitutes a privacy violation by broadcast or closed-circuit television and video systems. Fundamental to those proposals are the concepts of drone registration and the legalisation of the right to self-defence against drones. Registration requires that a drone is registered with the regulatory authorities, with a registered drone being traceable back to the owner of the drone. Registered drones may also be required to carry a remotely-readable identifier. Legalisation of self-defence allows bystanders to take defensive actions against drones, with the potential for a drone to be destroyed. Both of these mechanisms provide a means by which the operator of a drone faces some cost if they are causing harm, and thus may induce more efficient actions by the drone operator. This thesis establishes a theoretical framework for self-defence, registration, and registration in conjunction with self-defence. Conditions are established under which each will be the preferred form of regulation. It is also established that the status quo, with neither registration nor self-defence, is likely to be optimal when harm from drone activity is relatively low. The conditions established around when self-defence is efficient also provide the conditions for the regulation of counter-drone systems. I identify the legal impediments to the implementation of drone-detection systems and counter-drone systems in New Zealand, and propose a regulatory framework to allow the adoption of those systems.</p>