1. On rights and duties, you may be interested in Wesley Hohfeld's Fundamental Legal Conceptions (or a Debate Over Rights for a more recent exposition). It applies to both legal and moral rights. He distinguishes four senses the word right is used in usual terminology. 2. A (claim-)right proper is always correlated with a duty (that is how the term is usually defined). A right here means a position being deontically protected from being interfered. 3.The right to vote you guys discuss is in fact not a right proper, but a liberty (or privilege) to vote. It is correlated with the state of governance's rightlessness to require a citizen to vote. Much confusion is due to the different senses the word is used.