Any other kind of prohibition does not make an act illegal within the meaning of this section. Breach of a departmental order, for insance, is not illegal as the same is not covered under the expression ‘prohibited by law’. Similarly, refusing to perform such acts as charity or mercy is not illegal if the same is not prohibited by law. Thirdly, everything which furnishes ground for a civil action is illegal. Consequently, whenever someone does something for which an action can be brought in the Civil Court, his act is illegal under this section. Therefore, a breach of contract or a breach of trust is ‘illegal’ under this section since the same furnishes a ground for a civil action.
The expression ‘legally bound to do’ means whatever it is illegal in one to omit. The word ‘illegal’ used here has the same meaning as given above. Therefore, any omission on the part of someone which would make it an illegal omission, is such an act which he is legally bound to do.
In Mailsami v. State, the Madras High Court held that sexual intercourse between two unmarried persons with consent does not amount to illegal act under section 43 of the Code.