Not infrequently, it seems that the courts regard not-unlawful conduct as illegal in criminal cases. This problem is caused mainly by logical misunderstandings and misleading assumptions in criminal law. This paper therefore sheds light on the difference and relationship between unlawfulness and illegality.In the first part, the paper deals with the issue of whether there is a third possibility following neither legal nor illegal, that is Rechtsfreier Raum (e.g. the plank of Carneades, suicide, abortion, surrogacy, cloning, etc.). There is, at the very least, a logically neutral area between legal and illegal conduct. Hence, the courts should decide “illegal or not illegal" as with “guilty or not guilty", to exclude neutral conduct.The latter part attempts to provide a solution to the misleading assumption. According to most courts and academics, any conduct must be assumed illegal, only because it seemingly violates a penal provision, and must be regarded as illegal if it is not justified. To establish illegality, however, its grounds must be required to prevent the court from misjudging neutral conduct as illegal. Thus, it is necessary to prove the unlawfulness of the conduct. This means that only unlawful conduct shall be judged as illegal in a criminal case. This paper suggests that unlawfulness should be a prerequisite for illegality as a judicial conclusion in a criminal case. The issue of the nature of unlawfulness is also briefly discussed.