Conscience clause is a special legal regulation that enables the individual to refrain from certain actions, that he is obliged by the law, but which in his conviction, are contrary to his conscience. On one hand, this article shows that clause of conscience in contemporary legislation seems to be something natural because it gives the individual freedom of conscience, but on the other hand - some trends appear to legally narrow it or even to cancel the conscience clause. These trends appear in the context of contemporary tendencies against life. Presented analyses defend the conscience clause again and refer basically to medical professions. The base for this legal regulation constitutes the right to conscientious objection whereas this objection should always be constructive. Existence of the right to conscientious objection is confirmed by the analyses carried out on philosophical - ethical and theological -moral levels, and especially by the concept of natural right. The article also depicts that deep conviction of right to conscientious objection does mean that moral dilemmas concerning refusal to participation in evil do not exist. In some cases conscientious objection becomes contemporary form of martyrdom.