The creation by government regulation of entitlements akin to property rights is a widespread phenomenon imposing a reconsideration of the traditional categories of public and private property. The allocation of such rights that lack an explicit legislative definition but are object of relevant social and legal interests is a very complex topic, which has become very acute in cases where markets have been established for them. The analysis of the systems created for the allocation and management of these rights is the core of this book, which examines four emblematic examples: airport slots, spectrum rights, milk quotas and emission allowances. The book focuses on the European level, including legislation and the most relevant policy issues, by means of a comparative method involving private law, public law and law and economics approaches.