Nothing in this Act shall apply to or in relation to—
         (a) any person who was in any State and who had been expelled from that State or India before the commencement of this Act in that State or in relation to whose expulsion from such State or India any order made before such commencement under any other law is in force;
         (b) any person detected as a foreigner at the time of his entry across any border of India;
         (c) any foreigner who, having entered into India under a valid passport or travel document, continued to remain therein after the expiry of the period for which he was authorised to remain in India under such passport or travel document.