This paper examines the moral and legal issues of nudges. First, we review the definition of nudge and argue that it is important to view nudges as a matter of degree. This will also allow us to evaluate non-coercive and messaging kinds of laws in the light of nudging ethics. Next, we discuss the ethics of manipulation with respect to the moral issues of nudging. In order to consider the pros and cons of manipulation, it is necessary to examine conceptions such as liberty, welfare, rationality, autonomy, and legitimacy. In particular, transparency is important in nudging ethics, and we will investigate a contextualist approach that specifically identifies what aspects of nudges should be transparent.