The protection of Article 311 (2) for giving reasonable opportunity is not available in the following circumstances : (a) where a person is dismissed are reduced in rank on the ground of misconduct which has led to conviction or criminal charges ; (b) where it is impracticable to give the civil servant an opportunity to defend himself but the authority taking action against him shall record the reasons for such action ; (c) where in the interest of the security of state, it is not expedient to give such an opportunity to the civil servant [Article 311, proviso].